{"title":"Fish Pen","description":"\u003cdiv class=\"collection-description\"\u003e\n\u003ch1 class=\"page_heading\"\u003eFish Pen — Penicillin for Aquarium \u0026amp; Ornamental Fish\u003c\/h1\u003e\n\u003cp\u003eCalVetSupply's Fish Pen contains Penicillin — one of the oldest and most reliable gram-positive bacterial antibiotics available for ornamental and aquarium fish. Available in 250mg capsules, Fish Pen is a trusted choice for fish keepers dealing with gram-positive bacterial infections, fin rot, ulcers, and common bacterial conditions in freshwater ornamental fish that respond well to penicillin-class treatment.\u003c\/p\u003e\n\u003cp\u003eFish Pen is commonly used to treat fin rot, tail rot, open ulcers, bacterial skin infections, and gram-positive bacterial conditions in freshwater ornamental fish. Its penicillin-class action targets gram-positive bacterial cell walls — disrupting their structural integrity and stopping the infection from spreading further through your tank. Fish Pen is a dependable first-response antibiotic for fish keepers when gram-positive bacterial infections are suspected in freshwater aquarium fish.\u003c\/p\u003e\n\u003cp\u003eFish Pen works by binding to penicillin-binding proteins on bacterial cell walls — blocking the final stage of cell wall synthesis and causing bacterial cells to rupture and die. This targeted mechanism makes Fish Pen particularly effective against gram-positive pathogens commonly found in freshwater aquarium environments. All Fish Pen products at CalVetSupply are for ornamental aquarium fish use only and available without a vet prescription.\u003c\/p\u003e\n\u003ch2\u003eWhat Is Fish Pen?\u003c\/h2\u003e\n\u003cp\u003eFish Pen contains Penicillin, one of the most established antibiotic classes in fish care. It works by targeting and destroying gram-positive bacterial cell walls — preventing harmful bacteria from surviving and reproducing in your aquarium. Fish Pen 250mg is a reliable first-line antibiotic for ornamental freshwater fish dealing with gram-positive bacterial infections including fin rot, ulcers, and common bacterial skin conditions.\u003c\/p\u003e\n\u003ch2\u003eWhat Does Fish Pen Treat?\u003c\/h2\u003e\n\u003cp\u003eFish Pen is effective against fin rot, tail rot, open ulcers, bacterial skin infections, and gram-positive bacterial conditions in ornamental freshwater fish. It targets pathogens including Streptococcus and other gram-positive bacteria commonly responsible for external infections and tissue damage in aquarium fish. Fish Pen is best suited for freshwater fish — saltwater environments can reduce the effectiveness of penicillin-class antibiotics.\u003c\/p\u003e\n\u003ch2\u003eWhy Choose Fish Pen Over Other Fish Antibiotics?\u003c\/h2\u003e\n\u003cp\u003eFish Pen is the most targeted option for confirmed gram-positive bacterial infections in freshwater ornamental fish. While broader-spectrum antibiotics like Fish Mox (Amoxicillin) cover both gram-positive and gram-negative bacteria, Fish Pen delivers focused penicillin-class treatment specifically for gram-positive pathogens. It is a straightforward, reliable choice for fish keepers who have identified a gram-positive bacterial infection and want a direct, proven treatment option.\u003c\/p\u003e\n\u003ch2\u003eHow to Use Fish Pen for Aquarium Fish\u003c\/h2\u003e\n\u003cp\u003eRemove activated carbon from your filter before starting treatment — carbon absorbs medication and prevents it from reaching effective levels in your tank. Follow the dosage instructions on the product label carefully. Quarantine sick fish in a hospital tank when possible to protect your main tank's biological filtration and prevent the spread of infection to healthy fish. Complete the full treatment course even if symptoms improve early to prevent antibiotic resistance.\u003c\/p\u003e\n\u003ch2\u003eWhy Buy Fish Pen at CalVetSupply?\u003c\/h2\u003e\n\u003cp\u003eCalVetSupply offers Fish Pen 250mg at competitive prices with fast U.S. shipping and no vet prescription required for ornamental fish use. We provide clear ingredient and dosage information on every product listing so you can identify the right antibiotic and begin treatment without delay.\u003c\/p\u003e\n\u003ch2\u003eFAQ SECTION\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What is Fish Pen used for?\u003c\/strong\u003e A: Fish Pen (Penicillin 250mg) is used to treat fin rot, tail rot, open ulcers, bacterial skin infections, and gram-positive bacterial conditions in ornamental freshwater aquarium fish.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Do I need a prescription to buy Fish Pen?\u003c\/strong\u003e A: No. Fish Pen is available at CalVetSupply without a vet prescription. It is intended for ornamental aquarium fish use only.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What makes Fish Pen different from Fish Mox?\u003c\/strong\u003e A: Fish Pen contains Penicillin and targets gram-positive bacteria specifically. Fish Mox contains Amoxicillin — a broader-spectrum penicillin-class antibiotic that covers both gram-positive and gram-negative bacteria. Fish Pen is the more targeted option for confirmed gram-positive infections while Fish Mox provides wider coverage.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Is Fish Pen suitable for saltwater fish?\u003c\/strong\u003e A: Fish Pen is best suited for freshwater ornamental fish. Saltwater environments can reduce the effectiveness of penicillin-class antibiotics. For saltwater fish bacterial infections consider Fish Flox or Fish Zithro instead.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How long does Fish Pen treatment take?\u003c\/strong\u003e A: Most Fish Pen treatment courses run 7–10 days. Always complete the full course even if your fish shows early signs of recovery to prevent antibiotic resistance.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Will Fish Pen harm my tank's beneficial bacteria?\u003c\/strong\u003e A: Fish Pen may affect biological filtration in your tank. Treating sick fish in a separate hospital tank when possible helps minimize disruption to your main aquarium.\u003c\/p\u003e\n\u003c\/div\u003e","products":[{"product_id":"fish-pen","title":"Fish Pen (Fix Pen) Penicillin 500mg Fish Antibacterial","description":"\u003cstyle\u003e\n  .fph-product-copy {\n    --fph-orange: #e37111;\n    --fph-teal: #148d85;\n    --fph-green: #64ad82;\n    --fph-dark: #09213f;\n    --fph-text: #24374e;\n    --fph-muted: #64748b;\n    --fph-border: #dce3eb;\n    --fph-light: #f5f8fa;\n    --fph-teal-light: #eef8f6;\n    --fph-orange-light: #fff6ed;\n    --fph-white: #ffffff;\n\n    width: 100%;\n    max-width: 1675px;\n    margin: 0 auto;\n    padding-right: 40px;\n    padding-left: 40px;\n    color: var(--fph-text);\n    font-family: inherit;\n    font-size: 17px;\n    line-height: 1.7;\n    scroll-behavior: smooth;\n  }\n\n  .fph-product-copy,\n  .fph-product-copy * {\n    box-sizing: border-box;\n  }\n\n  .fph-product-copy section {\n    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var(--fph-border);\n    border-radius: 14px;\n    background: #fafbfc;\n    text-align: center;\n    font-weight: 700;\n  }\n\n  .fph-verification {\n    margin-top: 30px;\n    overflow: hidden;\n    border: 1px solid var(--fph-border);\n    border-radius: 20px;\n    background: var(--fph-white);\n  }\n\n  .fph-verification-header {\n    padding: 25px;\n    background: var(--fph-dark);\n    color: var(--fph-white);\n  }\n\n  .fph-verification-header h2 {\n    margin: 0 0 7px;\n    color: var(--fph-white);\n    font-size: 29px;\n  }\n\n  .fph-verification-header p {\n    margin: 0;\n    color: rgba(255, 255, 255, 0.88);\n  }\n\n  .fph-verification-body {\n    padding: 27px;\n  }\n\n  .fph-verification-grid {\n    display: grid;\n    grid-template-columns: repeat(2, minmax(0, 1fr));\n    gap: 18px;\n    margin: 24px 0;\n  }\n\n  .fph-verification-card {\n    padding: 23px;\n    border: 1px solid #cfe2df;\n    border-radius: 16px;\n    background: var(--fph-teal-light);\n  }\n\n  .fph-verification-card h3 {\n    margin: 0 0 9px;\n    color: var(--fph-teal);\n    font-size: 20px;\n  }\n\n  .fph-verification-card p {\n    margin: 0;\n  }\n\n  .fph-contact-link {\n    color: var(--fph-orange);\n    font-weight: 750;\n  }\n\n  .fph-educational-note {\n    margin-top: 24px;\n    padding: 20px 22px;\n    border-radius: 15px;\n    background: #eef3f7;\n    color: #42566d;\n    font-size: 15px;\n  }\n\n  .fph-reviewed {\n    margin-top: 18px;\n    color: var(--fph-muted);\n    font-size: 14px;\n  }\n\n  @media (max-width: 1050px) {\n    .fph-comparison-grid {\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n    }\n\n    .fph-benefits-grid,\n    .fph-related-grid {\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n    }\n  }\n\n  @media (max-width: 749px) {\n    .fph-product-copy {\n      padding-right: 18px;\n      padding-left: 18px;\n      font-size: 16px;\n      line-height: 1.65;\n    }\n\n    .fph-product-title {\n      font-size: 32px;\n    }\n\n    .fph-section {\n      padding: 39px 0;\n    }\n\n    .fph-section-title {\n      font-size: 28px;\n    }\n\n    .fph-toc-label {\n      display: none;\n    }\n\n    .fph-toc a {\n      min-height: 44px;\n      padding: 9px 17px;\n      font-size: 15px;\n    }\n\n    .fph-glance-row {\n      grid-template-columns: 1fr;\n    }\n\n    .fph-glance-label {\n      padding-bottom: 7px;\n    }\n\n    .fph-glance-value {\n      padding-top: 7px;\n    }\n\n    .fph-two-column,\n    .fph-comparison-grid,\n    .fph-benefits-grid,\n    .fph-timeline,\n    .fph-safety-grid,\n    .fph-policy-grid,\n    .fph-related-grid,\n    .fph-browse-grid,\n    .fph-verification-grid {\n      grid-template-columns: 1fr;\n    }\n\n    .fph-step {\n      grid-template-columns: 48px minmax(0, 1fr);\n      gap: 14px;\n      padding: 20px;\n    }\n  }\n\n  @media (prefers-reduced-motion: reduce) {\n    .fph-product-copy *,\n    .fph-product-copy *::before,\n    .fph-product-copy *::after {\n      transition: none !important;\n      animation: none !important;\n      scroll-behavior: auto !important;\n    }\n  }\n\u003c\/style\u003e\n\u003cdiv class=\"fph-product-copy\"\u003e\n\u003csection class=\"fph-section\" id=\"overview\"\u003e\n\u003ch1 class=\"fph-product-title\"\u003eFix Pen (Fish Pen Forte) Penicillin Tablets - 500 mg\u003c\/h1\u003e\n\u003cnav class=\"fph-toc\" aria-label=\"On this page\"\u003e\u003cspan class=\"fph-toc-label\"\u003eOn this page:\u003c\/span\u003e \u003ca href=\"#overview\"\u003eOverview\u003c\/a\u003e \u003ca href=\"#fish-pen-vs-fix-pen\"\u003eFish Pen vs Fix Pen\u003c\/a\u003e \u003ca href=\"#benefits\"\u003eBenefits\u003c\/a\u003e \u003ca href=\"#usage\"\u003eUsage\u003c\/a\u003e \u003ca href=\"#how-it-works\"\u003eHow It Works\u003c\/a\u003e \u003ca href=\"#safety\"\u003eSafety\u003c\/a\u003e \u003ca href=\"#shipping\"\u003eShipping\u003c\/a\u003e \u003ca href=\"#faq\"\u003eFAQ\u003c\/a\u003e \u003ca href=\"#bottom-line\"\u003eBottom Line\u003c\/a\u003e\u003c\/nav\u003e\n\u003cdiv class=\"fph-glance\"\u003e\n\u003cdiv class=\"fph-glance-heading\"\u003eFix Pen at a Glance\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-row\"\u003e\n\u003cdiv class=\"fph-glance-label\"\u003eFor\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-value\"\u003eOrnamental aquarium fish and non-food pet birds\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-row\"\u003e\n\u003cdiv class=\"fph-glance-label\"\u003eHelps with\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-value\"\u003eSuspected bacterial problems such as fin rot, tail rot, ulcers, infected wounds, and pop-eye\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-row\"\u003e\n\u003cdiv class=\"fph-glance-label\"\u003eForm\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-value\"\u003eTablets, 500 mg each\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-row\"\u003e\n\u003cdiv class=\"fph-glance-label\"\u003eCount sizes\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-value\"\u003e30-count and 60-count bottles\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-row\"\u003e\n\u003cdiv class=\"fph-glance-label\"\u003eWater type\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-value\"\u003eFreshwater and saltwater\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-row\"\u003e\n\u003cdiv class=\"fph-glance-label\"\u003eMade in\u003c\/div\u003e\n\u003cdiv class=\"fph-glance-value\"\u003eUnited States by Aqua Soma Labs\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cp class=\"fph-lead\"\u003e\u003cstrong\u003eFix Pen\u003c\/strong\u003e is an antibacterial treatment for ornamental aquarium fish and non-food pet birds.\u003c\/p\u003e\n\u003cp\u003eEach tablet contains 500 mg of Penicillin V Potassium and is manufactured in the United States by Aqua Soma Labs.\u003c\/p\u003e\n\u003cp\u003eFix Pen is available in bottles containing 30 or 60 tablets with clearly printed expiration dates.\u003c\/p\u003e\n\u003cp\u003eAquarium keepers may know this product under older names such as Fish Pen, Fish Pen Forte, Aqua Pen, or FISHBIOTIC Penicillin.\u003c\/p\u003e\n\u003cp\u003eThese were names associated with discontinued Thomas Labs products, while Fix Pen is the current Aqua Soma Labs replacement.\u003c\/p\u003e\n\u003cp\u003eAquarium keepers may consider penicillin tablets when ornamental fish show suspected bacterial signs such as fin and tail rot, mouth rot, infected wounds, pop-eye, cloudy eyes, open sores, ulcers, reddened skin, or columnaris-type lesions with a cotton-wool appearance.\u003c\/p\u003e\n\u003cp\u003ePenicillin V acts on the cell walls of certain susceptible bacteria and is generally associated with activity against Gram-positive bacteria and some Gram-negative organisms.\u003c\/p\u003e\n\u003cp\u003eFix Pen provides a consistent 500 mg tablet strength that can be dissolved in aquarium water or divided for a smaller treatment system.\u003c\/p\u003e\n\u003cp\u003eThe same tablets may be considered for non-food pet birds only under direct avian veterinary guidance.\u003c\/p\u003e\n\u003cp\u003eChoose the 30-count bottle for a single hospital tank or occasional use, or the 60-count bottle for larger aquarium collections, multi-tank operations, or a veterinarian-directed aviary treatment plan.\u003c\/p\u003e\n\u003cp\u003eBegin treatment at the first signs of a suspected bacterial concern. Symptoms differ between fish and birds, so review the separate lists below.\u003c\/p\u003e\n\u003cdiv class=\"fph-two-column\"\u003e\n\u003cdiv class=\"fph-info-box\"\u003e\n\u003ch3\u003eFish-Specific Symptoms\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eFin and tail rot with frayed or deteriorating fins\u003c\/li\u003e\n\u003cli\u003eMouth rot\u003c\/li\u003e\n\u003cli\u003eInfected wounds\u003c\/li\u003e\n\u003cli\u003ePop-eye or bulging eyes\u003c\/li\u003e\n\u003cli\u003eCloudy eyes\u003c\/li\u003e\n\u003cli\u003eColumnaris-type lesions with a cotton-wool appearance\u003c\/li\u003e\n\u003cli\u003eOpen sores, ulcers, or reddened skin\u003c\/li\u003e\n\u003cli\u003eReduced appetite, lethargy, or hiding\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-info-box\"\u003e\n\u003ch3\u003eBird-Specific Symptoms Under Veterinary Guidance\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eRespiratory signs with labored breathing\u003c\/li\u003e\n\u003cli\u003eSoft-tissue concerns linked by a veterinarian to bacteria\u003c\/li\u003e\n\u003cli\u003eFluffed-up feathers\u003c\/li\u003e\n\u003cli\u003eLethargy or inactivity\u003c\/li\u003e\n\u003cli\u003eDecreased appetite\u003c\/li\u003e\n\u003cli\u003eOther symptoms specifically evaluated by an avian veterinarian\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cp style=\"margin-top: 28px;\"\u003eFor birds, only use Fix Pen when an avian veterinarian has recommended penicillin for a specific condition and has determined the appropriate amount, administration method, frequency, and duration.\u003c\/p\u003e\n\u003cp\u003eStable water quality, appropriate nutrition, good housing, low stress, and careful observation remain essential parts of fish and bird care.\u003c\/p\u003e\n\u003cp\u003ePenicillin does not treat viral problems, and unnecessary antibacterial use may reduce treatment effectiveness over time.\u003c\/p\u003e\n\u003cdiv class=\"fph-order-note\"\u003e\n\u003cp\u003e\u003cstrong\u003eSame-day dispatch:\u003c\/strong\u003e In-stock orders placed before 1:30 p.m. CT, Monday through Friday, ship from our United States warehouse through USPS or UPS.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-highlight-note\"\u003e\n\u003cstrong\u003eImportant Notice:\u003c\/strong\u003e This product is intended for ornamental aquarium fish and non-food pet birds only. It is not intended for animals raised for food.\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"fish-pen-vs-fix-pen\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eFish Pen Forte vs Fix Pen: What Changed?\u003c\/h2\u003e\n\u003cp\u003eIf you previously purchased Thomas Labs Fish Pen, Fish Pen Forte, Aqua Pen, or FISHBIOTIC Penicillin, here is what remains the same and what has changed.\u003c\/p\u003e\n\u003cdiv class=\"fph-comparison-grid\"\u003e\n\u003cdiv class=\"fph-comparison-card\"\u003e\n\u003cspan class=\"fph-small-label\"\u003eActive ingredient\u003c\/span\u003e\n\u003ch3\u003eSame Penicillin Formula\u003c\/h3\u003e\n\u003cp\u003eFix Pen contains Penicillin V Potassium at 500 mg per tablet, matching the familiar strength associated with Fish Pen and Fish Pen Forte.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-comparison-card\"\u003e\n\u003cspan class=\"fph-small-label\"\u003eManufacturer\u003c\/span\u003e\n\u003ch3\u003eNew Manufacturer\u003c\/h3\u003e\n\u003cp\u003eFix Pen is manufactured in the United States by Aqua Soma Labs and replaces the discontinued Thomas Labs product line.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-comparison-card\"\u003e\n\u003cspan class=\"fph-small-label\"\u003eTablet format\u003c\/span\u003e\n\u003ch3\u003eSame Dissolvable Tablet Form\u003c\/h3\u003e\n\u003cp\u003eThe tablet can be dissolved in aquarium water or divided for smaller treatment volumes according to the current bottle label.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-comparison-card\"\u003e\n\u003cspan class=\"fph-small-label\"\u003eBottle options\u003c\/span\u003e\n\u003ch3\u003e30-Count and 60-Count Bottles\u003c\/h3\u003e\n\u003cp\u003eChoose the bottle size that fits a single hospital tank, repeat treatment, multi-tank aquarium setup, or veterinarian-directed aviary plan.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"benefits\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eBenefits of Fix Pen for Fish \u0026amp; Birds\u003c\/h2\u003e\n\u003cdiv class=\"fph-benefits-grid\"\u003e\n\u003cdiv class=\"fph-benefit-card\"\u003e\n\u003cdiv class=\"fph-benefit-number\"\u003e01\u003c\/div\u003e\n\u003ch3\u003eTargeted Gram-Positive Bacterial Coverage\u003c\/h3\u003e\n\u003cp\u003ePenicillin is commonly considered when a susceptible Gram-positive bacterial component is suspected in fin damage, mouth rot, sores, ulcers, pop-eye, or cloudy eyes.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-benefit-card\"\u003e\n\u003cdiv class=\"fph-benefit-number\"\u003e02\u003c\/div\u003e\n\u003ch3\u003eMade in the United States\u003c\/h3\u003e\n\u003cp\u003eFix Pen is manufactured in the United States by Aqua Soma Labs and supplied with clearly printed strength and expiration information.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-benefit-card\"\u003e\n\u003cdiv class=\"fph-benefit-number\"\u003e03\u003c\/div\u003e\n\u003ch3\u003eConsistent 500 mg Tablets\u003c\/h3\u003e\n\u003cp\u003eEach tablet provides a fixed 500 mg amount of Penicillin V Potassium, making treatment-water calculations easier across different aquarium volumes.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-benefit-card\"\u003e\n\u003cdiv class=\"fph-benefit-number\"\u003e04\u003c\/div\u003e\n\u003ch3\u003eCommon Aquarium Use Cases\u003c\/h3\u003e\n\u003cp\u003eAquarium keepers may consider Fix Pen for suspected bacterial fin damage, infected wounds, flexibacter-type concerns, ulcers, and other symptoms where a susceptible bacterial cause is likely.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-benefit-card\"\u003e\n\u003cdiv class=\"fph-benefit-number\"\u003e05\u003c\/div\u003e\n\u003ch3\u003eFreshwater and Saltwater Compatible\u003c\/h3\u003e\n\u003cp\u003eFix Pen may be used in properly prepared freshwater or saltwater treatment tanks according to the current product label.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-benefit-card\"\u003e\n\u003cdiv class=\"fph-benefit-number\"\u003e06\u003c\/div\u003e\n\u003ch3\u003eQuarantine-Friendly and Biofilter Aware\u003c\/h3\u003e\n\u003cp\u003eA separate hospital tank helps protect the display aquarium's beneficial bacteria, sensitive invertebrates, and healthy tank mates.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-benefit-card\"\u003e\n\u003cdiv class=\"fph-benefit-number\"\u003e07\u003c\/div\u003e\n\u003ch3\u003eVet-Directed Option for Pet Birds\u003c\/h3\u003e\n\u003cp\u003ePenicillin may be used for non-food pet birds only when an avian veterinarian has diagnosed the problem and established the appropriate treatment plan.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"usage\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eUsage Guidelines \u0026amp; Instructions\u003c\/h2\u003e\n\u003cdiv class=\"fph-summary-box\"\u003e\n\u003ch3\u003eQuick Usage Summary for Fish\u003c\/h3\u003e\n\u003cp\u003eUse one 500 mg tablet per 20 gallons or approximately 76 litres of treatment water.\u003c\/p\u003e\n\u003cp\u003eRepeat every 24 hours and perform a partial water change between treatments.\u003c\/p\u003e\n\u003cp\u003eContinue for 5 to 10 days and discontinue use if no improvement is seen after five days.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-steps\"\u003e\n\u003cdiv class=\"fph-step\"\u003e\n\u003cdiv class=\"fph-step-number\"\u003e1\u003c\/div\u003e\n\u003cdiv\u003e\n\u003ch3\u003eSet Up a Separate Treatment Area\u003c\/h3\u003e\n\u003cp\u003eTreat affected fish in a hospital or quarantine tank whenever possible.\u003c\/p\u003e\n\u003cp\u003eThis limits exposure of healthy tank mates and makes it easier to monitor treatment response, ammonia, nitrite, temperature, and oxygen levels.\u003c\/p\u003e\n\u003cp\u003eRemove activated carbon and other chemical filtration media and switch off UV sterilization during treatment.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-step\"\u003e\n\u003cdiv class=\"fph-step-number\"\u003e2\u003c\/div\u003e\n\u003cdiv\u003e\n\u003ch3\u003eDirections for Fish Aquariums\u003c\/h3\u003e\n\u003cp\u003eDissolve one 500 mg tablet in a clean cup of aquarium water.\u003c\/p\u003e\n\u003cp\u003eAdd the dissolved mixture evenly throughout the treatment tank for every 20 gallons or approximately 76 litres of actual treatment water.\u003c\/p\u003e\n\u003cp\u003eCalculate the real water volume after accounting for substrate, decorations, equipment, and fill level.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-step\"\u003e\n\u003cdiv class=\"fph-step-number\"\u003e3\u003c\/div\u003e\n\u003cdiv\u003e\n\u003ch3\u003eRepeat Every 24 Hours\u003c\/h3\u003e\n\u003cp\u003eRepeat treatment once every 24 hours according to the current bottle label.\u003c\/p\u003e\n\u003cp\u003ePerform a partial water change between treatments to maintain suitable water quality.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-step\"\u003e\n\u003cdiv class=\"fph-step-number\"\u003e4\u003c\/div\u003e\n\u003cdiv\u003e\n\u003ch3\u003eContinue for 5 to 10 Days\u003c\/h3\u003e\n\u003cp\u003eContinue treatment for the complete recommended period, even when the fish begin to improve, unless a qualified professional advises otherwise.\u003c\/p\u003e\n\u003cp\u003eStopping treatment too early may allow the suspected bacterial problem to return.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-step\"\u003e\n\u003cdiv class=\"fph-step-number\"\u003e5\u003c\/div\u003e\n\u003cdiv\u003e\n\u003ch3\u003eStop if There Is No Improvement\u003c\/h3\u003e\n\u003cp\u003eIf no improvement is seen after five days, discontinue treatment and reassess the water quality and likely cause.\u003c\/p\u003e\n\u003cp\u003eSeek aquatic veterinary or fish-health guidance if the fish become worse or develop severe distress.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-step\"\u003e\n\u003cdiv class=\"fph-step-number\"\u003e6\u003c\/div\u003e\n\u003cdiv\u003e\n\u003ch3\u003eMaintain Water Quality\u003c\/h3\u003e\n\u003cp\u003eMaintain strong aeration and stable temperature throughout treatment.\u003c\/p\u003e\n\u003cp\u003eTest ammonia and nitrite regularly because antibacterial treatment may disturb beneficial filtration.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-step\"\u003e\n\u003cdiv class=\"fph-step-number\"\u003e7\u003c\/div\u003e\n\u003cdiv\u003e\n\u003ch3\u003ePet Birds Under Veterinary Guidance Only\u003c\/h3\u003e\n\u003cp\u003eDo not use the aquarium-water chart to calculate an amount for birds.\u003c\/p\u003e\n\u003cp\u003eAn avian veterinarian must determine the correct amount according to species, weight, diagnosis, administration method, frequency, and duration.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003ch3 class=\"fph-subtitle\"\u003eFix Pen Amounts by Aquarium Size\u003c\/h3\u003e\n\u003cdiv class=\"fph-table-wrapper\"\u003e\n\u003ctable class=\"fph-table\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eTank volume\u003c\/th\u003e\n\u003cth\u003ePenicillin per use\u003c\/th\u003e\n\u003cth\u003e500 mg tablets\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e10 gallons (38 L)\u003c\/td\u003e\n\u003ctd\u003e250 mg\u003c\/td\u003e\n\u003ctd\u003e½ tablet or the equivalent measured dissolved portion\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e20 gallons (76 L)\u003c\/td\u003e\n\u003ctd\u003e500 mg\u003c\/td\u003e\n\u003ctd\u003e1 tablet\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e40 gallons (151 L)\u003c\/td\u003e\n\u003ctd\u003e1,000 mg\u003c\/td\u003e\n\u003ctd\u003e2 tablets\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e60 gallons (227 L)\u003c\/td\u003e\n\u003ctd\u003e1,500 mg\u003c\/td\u003e\n\u003ctd\u003e3 tablets\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e75 gallons (284 L)\u003c\/td\u003e\n\u003ctd\u003eApproximately 1,875 mg\u003c\/td\u003e\n\u003ctd\u003eApproximately 4 tablets\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-highlight-note\"\u003eThese amounts follow the supplied label guideline of one 500 mg tablet per 20 gallons or approximately 76 litres, which equals about 25 mg per gallon. Dose according to the actual treatment-water volume, not the number of fish. For aquariums under 20 gallons, dissolving a complete tablet in a measured amount of water and adding the correct fraction may be more accurate than dividing the tablet by hand. The current bottle label or instructions from an aquatic veterinarian take priority over this quick-reference chart.\u003c\/div\u003e\n\u003ch3 class=\"fph-subtitle\"\u003eWhat to Expect During Treatment\u003c\/h3\u003e\n\u003cdiv class=\"fph-timeline\"\u003e\n\u003cdiv class=\"fph-timeline-card\"\u003e\n\u003ch3\u003eDays 1 to 2\u003c\/h3\u003e\n\u003cp\u003eFish may hide, eat less, or produce slightly cloudy treatment water. Maintain the treatment schedule and keep aeration strong.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-timeline-card\"\u003e\n\u003ch3\u003eDays 3 to 5\u003c\/h3\u003e\n\u003cp\u003eLook for sores and red areas that stop spreading, returning appetite, improved activity, and steadier breathing.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-timeline-card\"\u003e\n\u003ch3\u003eDays 5 to 10\u003c\/h3\u003e\n\u003cp\u003eComplete the recommended treatment. Afterward, perform a partial water change and restore activated carbon to help clear remaining treatment.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-highlight-note\"\u003eReassess treatment at day five. If there is no improvement, or if the fish become worse, discontinue treatment and seek aquatic veterinary guidance.\u003c\/div\u003e\n\u003ch3 class=\"fph-subtitle\"\u003eWhat You Need for Treatment\u003c\/h3\u003e\n\u003cdiv class=\"fph-info-box\"\u003e\n\u003cul\u003e\n\u003cli\u003eA separate hospital or quarantine tank\u003c\/li\u003e\n\u003cli\u003eA suitable aquarium heater\u003c\/li\u003e\n\u003cli\u003eAn air stone or established sponge filter\u003c\/li\u003e\n\u003cli\u003eAn ammonia and nitrite test kit\u003c\/li\u003e\n\u003cli\u003eA suitable water conditioner or dechlorinator\u003c\/li\u003e\n\u003cli\u003eA small net for gentle transfer\u003c\/li\u003e\n\u003cli\u003eA clean cup for dissolving and measuring the treatment\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-pro-tip\"\u003e\n\u003cp\u003e\u003cstrong\u003ePro Tip:\u003c\/strong\u003e Dose according to the actual treated water volume rather than the aquarium's advertised capacity. Gravel, rocks, decorations, equipment, and the fill level reduce the amount of water inside the tank.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"how-it-works\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eHow Fix Pen Works\u003c\/h2\u003e\n\u003cp class=\"fph-lead\"\u003eEach Fix Pen tablet contains 500 mg of Penicillin V Potassium.\u003c\/p\u003e\n\u003cp\u003ePenicillin V works by interfering with the cell walls of certain susceptible bacteria.\u003c\/p\u003e\n\u003cp\u003eIt is generally associated with activity against certain Gram-positive bacteria and some Gram-negative organisms when used as directed in ornamental fish care.\u003c\/p\u003e\n\u003cp\u003eThe treatment is most appropriate when a susceptible bacterial cause is likely and should not be expected to treat fungal, viral, or parasitic conditions.\u003c\/p\u003e\n\u003cp\u003eEach tablet also contains standard inactive ingredients that hold the tablet together during storage and allow it to break apart and disperse in aquarium water.\u003c\/p\u003e\n\u003cp\u003eUse in non-food pet birds must follow the exact diagnosis and instructions of an avian veterinarian.\u003c\/p\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"safety\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eSafety and Tank Notes\u003c\/h2\u003e\n\u003cp\u003eWhen used according to the current label, Fix Pen usually causes no problems in ornamental aquarium fish.\u003c\/p\u003e\n\u003cp\u003eUnnecessary use, inaccurate amounts, combining multiple treatments, or prolonged treatment may increase stress and antibacterial resistance.\u003c\/p\u003e\n\u003cdiv class=\"fph-safety-grid\"\u003e\n\u003cdiv class=\"fph-safety-card\"\u003e\n\u003ch3\u003eFish\u003c\/h3\u003e\n\u003cp\u003eFish may temporarily hide, eat less, or appear mildly lethargic during treatment.\u003c\/p\u003e\n\u003cp\u003eIf severe distress develops, including rapid gill movement, surface gasping, loss of balance, rolling, or remaining on the bottom, stop treatment, increase aeration, and perform an appropriate partial water change.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-safety-card\"\u003e\n\u003ch3\u003eBirds\u003c\/h3\u003e\n\u003cp\u003eUse Fix Pen in non-food pet birds only under avian veterinary guidance.\u003c\/p\u003e\n\u003cp\u003eIf a bird becomes unusually lethargic, stops eating, develops breathing difficulty, or appears significantly worse, discontinue use and contact the veterinarian.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-safety-card\"\u003e\n\u003ch3\u003eInvertebrates\u003c\/h3\u003e\n\u003cp\u003eDo not use Fix Pen in display tanks containing shrimp, snails, corals, or other sensitive invertebrates whenever a separate treatment tank is available.\u003c\/p\u003e\n\u003cp\u003ePenicillin may harm sensitive species or disturb the aquarium ecosystem.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-safety-card\"\u003e\n\u003ch3\u003eBiofilter Awareness\u003c\/h3\u003e\n\u003cp\u003eAntibacterial treatment may affect beneficial filtration bacteria.\u003c\/p\u003e\n\u003cp\u003eMonitor ammonia and nitrite closely and perform partial water changes whenever necessary.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-safety-card\"\u003e\n\u003ch3\u003eFiltration During Treatment\u003c\/h3\u003e\n\u003cp\u003eRemove activated carbon and other chemical filtration media and switch off UV sterilization during treatment.\u003c\/p\u003e\n\u003cp\u003eRestore normal filtration after treatment is complete.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-safety-card\"\u003e\n\u003ch3\u003eDo Not Mix Treatments\u003c\/h3\u003e\n\u003cp\u003eDo not combine Fix Pen with other aquarium or bird treatments unless a qualified veterinarian specifically recommends the combination.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-warning\"\u003e\n\u003ch3\u003eImportant Safety Note\u003c\/h3\u003e\n\u003cp\u003eFix Pen is intended for ornamental aquarium fish and non-food pet birds only.\u003c\/p\u003e\n\u003cp\u003eIt is not intended for animals raised for food.\u003c\/p\u003e\n\u003cp\u003eStore tablets in their original, tightly closed container in a cool, dry place protected from direct sunlight, excessive heat, and moisture.\u003c\/p\u003e\n\u003cp\u003eKeep out of reach of children and animals.\u003c\/p\u003e\n\u003cp\u003eAlways follow the directions printed on the current product label.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"shipping\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eShipping \u0026amp; Returns\u003c\/h2\u003e\n\u003cdiv class=\"fph-policy-grid\"\u003e\n\u003cdiv class=\"fph-policy-card\"\u003e\n\u003ch3\u003eShipping Policy\u003c\/h3\u003e\n\u003cp\u003eOrders ship from our United States warehouse within one business day through USPS or UPS.\u003c\/p\u003e\n\u003cp\u003eIn-stock orders placed before 1:30 p.m. CT, Monday through Friday, may ship the same business day.\u003c\/p\u003e\n\u003cp\u003eShipping rates and estimated delivery times are calculated at checkout.\u003c\/p\u003e\n\u003ca href=\"http:\/\/www.calvetsupply.com\/pages\/shipping-policy\"\u003eReview Shipping Policy → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-policy-card\"\u003e\n\u003ch3\u003eRefund Policy\u003c\/h3\u003e\n\u003cp\u003eIf there is an issue with your order, eligible products may be returned or exchanged within 30 days according to the current store guidelines.\u003c\/p\u003e\n\u003cp\u003eReview the complete refund policy before returning any product.\u003c\/p\u003e\n\u003ca href=\"http:\/\/www.calvetsupply.com\/pages\/refund-policy\"\u003eReview Refund Policy → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"faq\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"fph-faq\"\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is Fix Pen used for?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen contains Penicillin V Potassium and is intended for certain suspected bacterial problems in ornamental aquarium fish, including fin and tail rot, mouth rot, infected wounds, ulcers, pop-eye, cloudy eyes, and some columnaris-type lesions.\u003c\/p\u003e\n\u003cp\u003eUse in non-food pet birds should occur only under avian veterinary guidance.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is the difference between Fish Pen Forte and Fix Pen?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen is the current Aqua Soma Labs replacement for discontinued Thomas Labs Fish Pen and Fish Pen Forte products. It provides the same 500 mg Penicillin V Potassium tablet strength with updated packaging.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eIs Fix Pen a replacement for FISHBIOTIC Penicillin or Aqua Pen?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen is presented as the current replacement for older FISHBIOTIC Penicillin and Aqua Pen aquarium products.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow soon should I see improvement with Fix Pen?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eImprovement may appear within three to five days through sores that stop spreading, improved appetite, increased activity, and steadier breathing.\u003c\/p\u003e\n\u003cp\u003eDiscontinue treatment and seek professional advice if the fish worsen or no improvement appears by day five.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhere can I buy penicillin tablets for fish online?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen 500 mg tablets can be ordered through this online store in 30-count or 60-count bottles and shipped according to the current store shipping policy.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is in each Fix Pen tablet?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eEach tablet contains 500 mg of Penicillin V Potassium together with standard inactive tablet ingredients.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is the Fix Pen amount for fish?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eThe supplied label guideline is one 500 mg tablet per 20 gallons or approximately 76 litres of treatment water.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow long should I treat with Fix Pen?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eThe supplied instructions describe treatment every 24 hours for 5 to 10 days, with a partial water change between treatments.\u003c\/p\u003e\n\u003cp\u003eDiscontinue treatment if no improvement is seen after five days.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eShould I treat in the main tank or a hospital tank?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eA separate hospital or quarantine tank is strongly preferred. This protects healthy tank mates, sensitive invertebrates, and the display aquarium's established filtration.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eDo I need to remove activated carbon or turn off UV?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eRemove activated carbon and other chemical filtration media and switch off UV sterilization during treatment because these systems may reduce treatment availability in the water.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWill Fix Pen harm beneficial aquarium bacteria?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eAntibacterial treatment may disturb beneficial biological filtration. Use a separate treatment tank whenever possible and monitor ammonia and nitrite closely.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan Fix Pen be used in saltwater aquariums?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen is presented for properly prepared freshwater and saltwater treatment tanks. Use a separate hospital tank when the display system contains corals or sensitive invertebrates.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eIs Fix Pen safe for betta fish and small aquariums?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eSmall aquariums require careful measurement. The supplied rate is one 500 mg tablet per 20 gallons, so a smaller treatment volume requires a proportional amount.\u003c\/p\u003e\n\u003cp\u003eDissolving one tablet in a measured volume and adding the appropriate fraction may be more accurate than dividing the tablet by hand.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan I use Fix Pen in a planted tank or with shrimp and snails?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eTreat affected fish in a separate hospital tank whenever possible. Penicillin may disturb the display aquarium and may harm shrimp, snails, or other sensitive invertebrates.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan Fix Pen treat fungal, viral, or parasitic infections?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen is an antibacterial product and should not be expected to treat fungal, viral, or parasitic conditions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan I combine Fix Pen with other fish treatments?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eDo not combine Fix Pen with other aquarium treatments unless a qualified veterinarian specifically recommends the combination.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat should I do after finishing a Fix Pen treatment?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003ePerform a partial water change, resume normal filtration, restore activated carbon if normally used, and continue monitoring ammonia, nitrite, temperature, and fish behavior.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan I use Fix Pen for dogs, cats, or chickens?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eNo. This product is labeled for ornamental aquarium fish and non-food pet birds. It is not intended for dogs, cats, humans, chickens raised for food, or other food-producing animals.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan I use Fix Pen as penicillin for pet birds?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen may be considered for non-food pet birds only under direct avian veterinary guidance. The veterinarian must establish the diagnosis, amount, administration method, frequency, and duration.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow should I store and dispose of Fix Pen tablets?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eStore tablets tightly closed in their original container in a cool, dry location protected from direct sunlight, excessive heat, and moisture.\u003c\/p\u003e\n\u003cp\u003eFollow the current product label and applicable local requirements when disposing of unused tablets, treatment water, or filter media. Avoid releasing concentrated treatment into natural waterways.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\" id=\"bottom-line\"\u003e\n\u003cdiv class=\"fph-bottom-line\"\u003e\n\u003ch2\u003eBottom Line\u003c\/h2\u003e\n\u003cp\u003eFix Pen is a 500 mg Penicillin V Potassium tablet for certain suspected bacterial problems in ornamental aquarium fish and a veterinarian-directed penicillin option for non-food pet birds.\u003c\/p\u003e\n\u003cp\u003eIt is the current Aqua Soma Labs replacement for discontinued Thomas Labs Fish Pen and Fish Pen Forte products.\u003c\/p\u003e\n\u003cp\u003eThe supplied aquarium guideline is one 500 mg tablet per 20 gallons or approximately 76 litres of treatment water, repeated every 24 hours for 5 to 10 days with partial water changes between treatments.\u003c\/p\u003e\n\u003cp\u003eReassess treatment at day five and discontinue use if no improvement is seen.\u003c\/p\u003e\n\u003cp\u003eFix Pen will not treat fungal, viral, or parasitic conditions and is not intended for animals raised for food.\u003c\/p\u003e\n\u003cp\u003eUse a hospital tank whenever possible and consult an aquatic or avian veterinarian when the diagnosis is uncertain or when treating a bird.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\"\u003e\n\u003ch2 class=\"fph-section-title\"\u003eMore Fish \u0026amp; Bird Treatments\u003c\/h2\u003e\n\u003cdiv class=\"fph-related-grid\"\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Mox (Amoxicillin) 250\/500 mg\u003c\/h3\u003e\n\u003cp\u003eA treatment for fin rot, dropsy, ulcers, infected wounds, and other suspected bacterial concerns in ornamental fish.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-mox\"\u003eShop Fix Mox → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Zole (Metronidazole) 250\/500 mg\u003c\/h3\u003e\n\u003cp\u003eA treatment for certain anaerobic and protozoal concerns, including Hexamita and hole-in-the-head symptoms.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-zole\"\u003eShop Fix Zole → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Doxy (Doxycycline) 100 mg\u003c\/h3\u003e\n\u003cp\u003eA treatment for columnaris, respiratory concerns, and Mycoplasma-related problems in ornamental fish and non-food pet birds.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-doxy\"\u003eShop Fix Doxy → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Zithro (Azithromycin) 250 mg\u003c\/h3\u003e\n\u003cp\u003eA treatment for fin rot, columnaris, gill disease, and veterinarian-directed avian respiratory concerns.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-zithro\"\u003eShop Fix Zithro → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Cin (Clindamycin) 150 mg\u003c\/h3\u003e\n\u003cp\u003eA treatment for certain bacterial skin, mouth, wound, and soft-tissue concerns in ornamental aquarium fish.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-cin\"\u003eShop Fix Cin → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Sulfa (SMZ\/TMP) 960 mg\u003c\/h3\u003e\n\u003cp\u003eA dual-ingredient treatment used for a range of suspected bacterial concerns in ornamental aquarium fish.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-sulfa\"\u003eShop Fix Sulfa → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Flex (Cephalexin) 250\/500 mg\u003c\/h3\u003e\n\u003cp\u003eA treatment for fin rot, ulcers, infected wounds, and bacterial skin concerns in ornamental fish and non-food pet birds.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-flex\"\u003eShop Fix Flex → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-related-card\"\u003e\n\u003ch3\u003eFix Flox (Ciprofloxacin) 500 mg\u003c\/h3\u003e\n\u003cp\u003eA treatment for suspected bacterial concerns including fin rot, ulcers, columnaris-type patches, and septicemia.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/products\/fish-flox\"\u003eShop Fix Flox → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-browse-grid\"\u003e\n\u003cdiv class=\"fph-browse-card\"\u003e\n\u003ch3\u003eBrowse All Treatments\u003c\/h3\u003e\n\u003cp\u003eExplore the complete Fish \u0026amp; Bird Treatments Collection for additional Fix line products and related care options.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/collections\/fish-antibiotics\"\u003eExplore the Collection → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-browse-card\"\u003e\n\u003ch3\u003eGuides and Care Tips\u003c\/h3\u003e\n\u003cp\u003eVisit the Fish \u0026amp; Bird Care Blog for practical aquarium guides, water-care information, and treatment tips.\u003c\/p\u003e\n\u003ca href=\"https:\/\/www.calvetsupply.com\/blogs\/fish-antibiotics\"\u003eVisit the Blog → \u003c\/a\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-image-note\"\u003eTap the product image above to expand and zoom 🔍\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"fph-section\"\u003e\n\u003cdiv class=\"fph-verification\"\u003e\n\u003cdiv class=\"fph-verification-header\"\u003e\n\u003ch2\u003eTransparency \u0026amp; Verification\u003c\/h2\u003e\n\u003cp\u003eHow Product Information Is Verified\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-verification-body\"\u003e\n\u003cp\u003e\u003cstrong\u003eWho is responsible for this page:\u003c\/strong\u003e The store editorial team responsible for reviewing and maintaining product information.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eVerification snapshot:\u003c\/strong\u003e This page is written from the current product label for this item and reviewed for accuracy and consistency before publishing.\u003c\/p\u003e\n\u003ch3 class=\"fph-subtitle\"\u003eHow We Verify Product Information\u003c\/h3\u003e\n\u003cdiv class=\"fph-verification-grid\"\u003e\n\u003cdiv class=\"fph-verification-card\"\u003e\n\u003ch3\u003eLabel-First Accuracy\u003c\/h3\u003e\n\u003cp\u003eDirections, treatment duration, storage information, and warnings are taken from the current product label.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-verification-card\"\u003e\n\u003ch3\u003eSpecification Validation\u003c\/h3\u003e\n\u003cp\u003eThe active ingredient, tablet strength, bottle counts, and manufacturer information are cross-checked against available product specifications.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-verification-card\"\u003e\n\u003ch3\u003eConsistency Checks\u003c\/h3\u003e\n\u003cp\u003eProduct content is reviewed for consistent strength information, directions, storage details, and safety language throughout the page.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-verification-card\"\u003e\n\u003ch3\u003eUpdates\u003c\/h3\u003e\n\u003cp\u003ePages are updated when product labels, packaging, tablet counts, manufacturer details, or directions change.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-highlight-note\"\u003e\n\u003cstrong\u003eWhat we do not do:\u003c\/strong\u003e We do not invent product claims, and we do not add usage directions beyond what the current product label states for its intended use.\u003c\/div\u003e\n\u003cp style=\"margin-top: 25px;\"\u003eSee something that does not match the product you received? Please \u003cstrong\u003e\u003cspan style=\"color: rgb(255, 128, 0);\"\u003e\u003ca href=\"%20https:\/\/www.calvetsupply.com\/pages\/contact-us\" style=\"color: rgb(255, 128, 0);\"\u003econtact us\u003c\/a\u003e\u003c\/span\u003e\u003c\/strong\u003e so the information can be reviewed and updated.\u003c\/p\u003e\n\u003cdiv class=\"fph-educational-note\"\u003e\n\u003cstrong\u003eEducational use:\u003c\/strong\u003e This content is provided for general informational purposes only and is not a substitute for advice from a qualified veterinarian.\u003c\/div\u003e\n\u003cdiv class=\"fph-reviewed\"\u003eLast reviewed: July 10, 2026\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003c\/div\u003e","brand":"Aqua Soma Labs","offers":[{"title":"500-mg (30 Count)","offer_id":45972965818402,"sku":"641666","price":34.99,"currency_code":"USD","in_stock":true},{"title":"500-mg (60 Count)","offer_id":45972965851170,"sku":"811298","price":89.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0891\/7008\/3874\/files\/FishPen.png?v=1783911323"}],"url":"https:\/\/calvetsupply.com\/collections\/fish-pen.oembed","provider":"Calvetsupply","version":"1.0","type":"link"}