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Fish Zithro (Fix Zithro) Azithromycin Tablets - 250 mg
Fix Zithro at a Glance
For
Ornamental aquarium fish & non-food pet birds
Helps with
Fin and tail rot, columnaris, gill disease, and early respiratory signs in birds
Form
Crushable tablets, 250 mg each
Count sizes
12-count and 30-count bottles
Water type
Freshwater and saltwater
Made in
United States by Aqua Soma Labs
Fish Zithro (Fix Zithro) supplies 250 mg of azithromycin per tablet and is an antibacterial treatment for ornamental aquarium fish and non-food pet birds.
It is often selected to help manage suspected bacterial problems such as fin and tail rot, columnaris, gill disease, and early respiratory signs in pet birds.
Often called Bird Zithro or Fish Zithro in the hobby community, Fix Zithro is a replacement for the discontinued Thomas Labs Bird Zithro, Fish Zithro, and Aqua Zithro 250 mg products.
This azithromycin tablet from the Aqua Soma Labs Fix range is used for common problems such as fin and tail rot, columnaris, gill disease, bacterial hemorrhagic septicemia, and other bacterial infections in freshwater and saltwater aquariums.
Bird keepers may also use it under veterinary guidance for mild upper respiratory tract infections, suspected Mycoplasma concerns, or conditions associated with Chlamydia psittaci, including psittacosis, parrot fever, and ornithosis in pigeons and other pet birds.
Azithromycin helps slow or stop the growth of certain bacteria affecting the gills, skin, and respiratory tract.
When used as directed, it works best alongside appropriate husbandry, clean water, stable environmental conditions, and suitable nutrition.
Fix Zithro from Aqua Soma Labs is available in bottles of 12 or 30 tablets with fresh expiration dates.
The two bottle sizes provide flexible options for hobbyists maintaining a single hospital tank, several community aquariums, or an aviary under veterinary guidance.
Use Fix Zithro when early signs of bacterial stress appear. Symptoms may differ between fish and birds, so the lists below separate the most common signs by species.
Fish-Specific Symptoms
Clamped or frayed fins associated with fin and tail rot
Red or cloudy patches on the body
Fuzzy patches that may suggest columnaris
Pop-eye or exophthalmia
Gill irritation or labored gill movement
Secondary bacterial problems around gill-fluke damage
Listlessness or persistent appetite loss
Bird-Specific Symptoms
Sneezing or nasal discharge
Upper respiratory tract infection signs
Swollen eyes or sinus irritation
Suspected Mycoplasma-related concerns
Signs associated with Chlamydia psittaci or parrot fever
Ruffled feathers or a fluffed-up posture
Reduced activity or appetite loss
Address suspected bacterial problems early, maintain clean water, and consult an aquatic or avian professional whenever one is available.
Combining treatment with proper husbandry gives fish and birds a better opportunity to recover while helping keep the aquarium or aviary stable.
Order online for same-day dispatch on qualifying orders placed before 1:30 p.m. CT, Monday through Friday. Fix Zithro ships directly from our United States warehouse through USPS or UPS.
Important Notice: This product is intended for aquarium and ornamental fish and non-food pet birds only. It is not for animals used for food.
Bird Zithro vs Fix Zithro: What Changed?
If you previously purchased Thomas Labs Bird Zithro, Fish Zithro, or Aqua Zithro, here is what has changed and what remains the same.
Active ingredient
Same Azithromycin, Same Strength
Fix Zithro contains the same 250 mg of azithromycin per tablet associated with Bird Zithro, Fish Zithro, and Aqua Zithro.
Manufacturer
New Manufacturer
Fix Zithro is made by Aqua Soma Labs in the United States, replacing the discontinued Thomas Labs product line.
Tablet format
Same Crushable Tablet Form
Fix Zithro uses a crushable tablet format that can be dissolved in aquarium water or administered to birds exactly as directed by an avian veterinarian.
Bottle sizes
12-Count and 30-Count Options
Choose a 12-count bottle for smaller setups or occasional use, or a 30-count bottle for multiple tanks or veterinarian-directed aviary management.
Benefits of Fix Zithro for Fish & Birds
01
Bacterial Support for Fish & Birds
Fix Zithro provides azithromycin for ornamental fish and non-food pet birds. It may help manage fin and tail rot, columnaris, gill disease, and early respiratory or ornithosis-complex signs when used as directed.
02
Ready to Use Promptly
Keeping Fix Zithro properly stored means treatment is available when early bacterial signs appear. Avian use should still follow professional veterinary guidance.
03
Helps With Internal and External Problems
Azithromycin may be used for skin lesions, ulcers, fin damage, and internal bacterial concerns in a hospital tank, as well as part of a veterinarian-directed plan for respiratory or Mycoplasma-related concerns in birds.
04
Consistent 250 mg Tablets
Each tablet contains a consistent 250 mg amount, simplifying treatment calculations across different aquarium volumes.
05
Easy to Prepare
Crushable tablets can be dissolved in aquarium water or administered to birds in the exact form and amount directed by an avian veterinarian.
06
Freshwater, Saltwater & Aviary Setups
Fix Zithro can be used in properly prepared freshwater or marine treatment systems and may be considered for pigeons and ornamental birds under veterinary supervision.
07
Ideal for Hospital Tanks and Quarantine
A separate hospital tank or treatment enclosure reduces unnecessary exposure of healthy animals and allows more accurate observation and treatment control.
Usage Guidelines & Instructions
Directions for Use:
1
Set Up a Separate Treatment Area
Move affected fish to a dedicated hospital or quarantine tank.
Where practical, birds requiring treatment should be separated into an appropriate treatment enclosure under veterinary guidance.
Separation helps protect healthy tank mates or flock members and allows more accurate observation and treatment.
2
Directions for Fish Aquariums
Dissolve one 250 mg tablet per 10 gallons or 38 litres of water in the hospital tank.
Mix the tablet in a clean cup of aquarium water first, then distribute the prepared solution evenly around the treatment tank.
Repeat the treatment every 24 hours for 5 to 7 days while closely monitoring water quality and fish behavior.
Follow the current bottle label or an aquatic veterinarian's instructions when they differ from this quick-reference information.
3
Use in Pet Birds Under Veterinary Guidance
Administer Fix Zithro to pigeons and other non-food pet birds only under the direction of an avian veterinarian.
The veterinarian should determine the correct amount for the bird's species, weight, condition, frequency, and treatment duration.
Tablets may be given whole, divided, or crushed and mixed with food or drinking water only as specifically instructed.
4
Maintain Water Quality & Finish Treatment
Perform partial water changes when needed between treatments to keep ammonia and nitrite low.
Maintain strong aeration throughout treatment.
Continue for the complete recommended duration, even if the animal appears better, unless a veterinarian advises otherwise.
If no improvement appears after several days, or symptoms worsen, consult an aquatic or avian professional.
Fix Zithro Amounts by Aquarium Size
Tank volume
Azithromycin per use
250 mg tablets
10 gallons (38 L)
250 mg
1 tablet
20 gallons (76 L)
500 mg
2 tablets
30 gallons (114 L)
750 mg
3 tablets
40 gallons (151 L)
1,000 mg
4 tablets
55 gallons (208 L)
Approximately 1,375 mg
5 to 6 tablets
These figures follow the supplied guideline of one 250 mg tablet per 10 gallons, approximately 25 mg per gallon. Dose according to the actual treatment-tank water volume, not the number of fish. The current bottle label or your aquatic veterinarian's directions take priority over this quick-reference chart.
Amounts for Pet Birds
Bird amounts are determined by body weight rather than aquarium-water volume, so there is no universal bird chart.
The appropriate amount depends on the species, body weight, condition being treated, administration method, and overall health of the bird.
An avian veterinarian must determine the amount, frequency, and duration.
Do not estimate an avian amount independently or use the aquarium chart for birds.
What to Expect During Treatment
Days 1 to 2
Fish may hide or eat less, and treatment water may look slightly cloudy. Maintain the treatment schedule and keep aeration strong.
Days 3 to 5
Look for fin damage or red patches that stop spreading, returning appetite, and steadier breathing. Seek professional guidance if the fish worsen or no improvement appears by day five.
Days 5 to 7
Complete the recommended treatment even when improvement appears. Afterward, perform a partial water change and restore activated carbon.
What You Need for Treatment
Prepare the following supplies before starting treatment:
A separate hospital or quarantine tank
A heater suitable for the fish species
An air stone or established sponge filter
An ammonia and nitrite test kit
A suitable aquarium dechlorinator
A small net for careful transfer
A clean cup for dissolving each tablet
Pro Tip: Quarantine affected fish and birds away from healthy companions whenever practical. A dedicated treatment setup makes observation, water changes, and treatment control easier while reducing unnecessary exposure.
How Fix Zithro Works
Azithromycin is the active ingredient in Fix Zithro, supplied at 250 mg per tablet.
In practical terms, azithromycin helps slow or stop the growth of certain susceptible bacteria affecting the gills, skin, and respiratory tract of ornamental fish and non-food pet birds.
The remainder of each tablet consists of standard inactive ingredients that help hold the tablet together, maintain stability during storage, and allow the tablet to disperse when mixed with aquarium water.
Bird administration should follow the exact preparation and delivery method supplied by an avian veterinarian.
Safety and Tank Notes
When used as directed, Fix Zithro generally causes no problems in ornamental fish and non-food pet birds.
Incorrect amounts, unnecessarily prolonged use, or repeated antibacterial treatment can increase the risk of side effects and antibacterial resistance.
Fish
Azithromycin-based aquarium treatment may cause temporary hiding, mild water cloudiness, reduced activity, or decreased appetite.
If severe distress appears, including rapid gill movement, loss of balance, surface gasping, or remaining on the bottom, stop treatment, improve aeration, perform an appropriate water change, and seek aquatic veterinary advice.
Birds
Possible reactions may include reduced appetite, loose or changed droppings, and lethargy, particularly when the amount is too high or the bird is sensitive.
If a bird becomes fluffed up, inactive, has difficulty breathing, or stops eating, discontinue treatment and contact an avian veterinarian.
Invertebrates
Do not use Fix Zithro in display aquariums containing shrimp, snails, corals, or other sensitive invertebrates whenever a separate treatment tank is available.
Strong antibacterial treatments may harm sensitive species or disrupt the aquarium ecosystem.
Safe Use in Your System
Treat fish in a hospital or quarantine tank whenever possible.
Remove activated carbon and switch off UV sterilization during treatment. Monitor ammonia, nitrite, oxygen, and temperature closely.
Do not combine Fix Zithro with other antibacterial products unless specifically advised by a veterinarian.
Important Safety Warning
Fix Zithro is intended for ornamental aquarium fish and non-food pet birds only. It is not intended for animals raised for food.
Store tablets in their original container in a cool, dry location protected from direct sunlight, excessive heat, and moisture.
Keep the container tightly closed and out of reach of children and animals.
Always follow the directions printed on the current product label.
Shipping & Returns
Shipping Policy
Orders ship from our United States warehouse within one business day through USPS or UPS.
Same-day dispatch may be available for qualifying orders placed before 1:30 p.m. CT, Monday through Friday.
Shipping rates and estimated delivery times are calculated at checkout.
Fix Zithro contains azithromycin and is used for certain bacterial concerns in ornamental aquarium fish. These may include fin and tail rot, columnaris, gill disease, red or cloudy body areas, and certain internal bacterial problems.
In non-food pet birds, it may form part of a veterinarian-directed plan for certain respiratory, Mycoplasma-related, or Chlamydia psittaci concerns.
What is the difference between Bird Zithro and Fix Zithro?
Fix Zithro is the current Aqua Soma Labs product replacing discontinued Thomas Labs Bird Zithro and Fish Zithro products. It provides the familiar 250 mg azithromycin tablet strength in updated packaging.
Is Fix Zithro a replacement for Aqua Zithro?
Fix Zithro is presented as the current Aqua Soma Labs replacement for older Aqua Zithro products and provides 250 mg of azithromycin per tablet.
Is Fix Zithro the same as Fish Zithro?
Fix Zithro is intended as the updated replacement for discontinued Fish Zithro products, with the same 250 mg azithromycin tablet strength and updated branding.
Where can I buy azithromycin for fish online?
Fix Zithro 250 mg tablets can be ordered through this online store in 12-count or 30-count bottles and shipped according to the current store shipping policy.
Is azithromycin stronger than amoxicillin for fish?
Azithromycin and amoxicillin are different antibacterial ingredients with different activity profiles. One is not automatically better or stronger for every infection. The appropriate choice depends on the suspected organism and the condition being treated.
How do I know if my fish might need azithromycin?
Possible bacterial signs include frayed fins, fuzzy or red body patches, cloudy areas, gill irritation, pop-eye, appetite loss, and reduced activity.
Similar signs may also be caused by parasites, fungal conditions, injuries, or poor water quality, so professional assessment is recommended when the cause is unclear.
Is azithromycin for birds the same as fish azithromycin?
Fix Zithro contains azithromycin, but bird administration is based on body weight, species, condition, and veterinary instructions. Aquarium calculations must not be used for birds.
What size aquarium can one Fix Zithro tablet treat?
The supplied aquarium guideline uses one 250 mg tablet per 10 gallons or approximately 38 litres of treatment water.
Is fish azithromycin available in 500 mg?
This Fix Zithro product is supplied in a 250 mg tablet strength. A 500 mg treatment amount would require two 250 mg tablets according to the supplied aquarium chart.
How long should I treat with Fix Zithro?
The supplied directions describe one treatment every 24 hours for approximately 5 to 7 days. Always follow the current bottle label or veterinary instructions.
How soon should I see improvement?
Improvement may appear within three to five days through steadier breathing, returning appetite, improved activity, and bacterial lesions that stop spreading.
Seek professional advice if the animal becomes worse or no improvement appears after several days.
What should I do after finishing treatment?
Follow the product label, perform an appropriate partial water change, and restore activated carbon if normally used. Continue monitoring water quality and the condition of the treated fish.
Can I use Fix Zithro in my main community or reef tank?
A separate hospital tank is preferred. This reduces unnecessary exposure of healthy fish and sensitive invertebrates and helps protect the display aquarium's biological filtration.
Does Fix Zithro work in saltwater aquariums?
Fix Zithro is presented for use in properly prepared freshwater and saltwater treatment tanks. A separate hospital tank is especially important for marine systems containing corals or invertebrates.
Can Fix Zithro be used for racing pigeons?
Fix Zithro may be considered for non-food pet birds, including racing pigeons, only under the direction of an avian veterinarian who determines the correct amount and duration.
Can I combine Fix Zithro with other fish treatments?
Do not combine Fix Zithro with other antibacterial or aquarium treatments unless a qualified veterinarian specifically recommends the combination.
Can Fix Zithro treat fungal, viral, or parasitic infections?
Fix Zithro is an antibacterial product. It should not be expected to treat fungal, viral, or parasitic conditions unless a professional has identified a separate appropriate reason for its use.
Is Fix Zithro safe for betta fish and small aquariums?
Small aquariums require careful volume calculations. The supplied guide is one 250 mg tablet per 10 gallons, so a smaller tank may require an accurately divided amount. Follow the bottle label or consult an aquatic veterinarian rather than estimating.
How should I store and dispose of Fix Zithro tablets?
Store tablets tightly closed in a cool, dry place protected from direct sunlight and moisture.
Follow the current label and applicable local requirements when disposing of unused tablets, treatment water, or filter media. Avoid releasing concentrated treatment into natural waterways.
More Fish & Bird Treatments
Fix Mox (Amoxicillin) 250/500 mg
A treatment for fin rot, dropsy, ulcers, and other bacterial concerns in ornamental fish. Available in 30-count and 100-count capsules.
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Transparency & Verification
How Product Information Is Verified
Who is responsible for this page: The store editorial team responsible for reviewing and maintaining product information.
Verification snapshot: This page is written from the current product label for this item and reviewed for accuracy and consistency before publishing.
How We Verify Product Information
Label-First Accuracy
Directions, duration, storage information, and warnings are taken from the current product label for this item.
Specification Validation
Key details such as the active ingredient, tablet strength, and bottle counts are cross-checked against available manufacturer specifications.
Consistency Checks
Product content is reviewed for consistent strengths, directions, safety information, and storage details throughout the page.
Updates
Pages are updated when the product label, packaging, tablet count, manufacturer information, or directions change.
What we do not do: We do not invent product claims, and we do not add usage directions beyond what the current product label states for its intended use.
See something that does not match the product you received? Please contact usso the information can be reviewed and updated.
Educational use: This content is provided for general informational purposes only and is not a substitute for advice from a qualified veterinarian.
