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Fish Zole (Fix Zole) Metronidazole 250mg & 500mg Fish Antibacterial

$40.99
by Aqua Soma Labs
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Fish Zole (Fix Zole) Metronidazole Tablets, Fish & Bird Antibacterial 250 mg / 500 mg

Fix Zole at a Glance
For
Ornamental aquarium fish & non-food pet birds
Helps with
Internal parasites and protozoan flagellates such as Hexamita and Spironucleus
Form
Tablets, 250 mg or 500 mg each
Count sizes
60-count bottles
Water type
Freshwater or saltwater treatment tanks
Made in
United States by Aqua Soma Labs

Fish Zole (Fix Zole) is a metronidazole antibacterial treatment in tablet form for ornamental aquarium fish and non-food pet birds.

Each tablet supplies 250 mg or 500 mg of metronidazole and is made in the United States by Aqua Soma Labs. Hobbyists commonly use it to help manage suspected protozoan problems in a hospital or quarantine tank, where dosing and observation are easier to control.

Aquarists have known this metronidazole tablet under earlier names, including the discontinued Thomas Labs Fish Zole and Fish Zole Forte, Aqua-Zole, fishzole, and fishbiotic metronidazole.

Fix Zole is the current Aqua Soma Labs version, replacing those older products with the same metronidazole strengths of 250 mg or 500 mg per tablet. Keepers who previously used MetroPlex may find this a convenient tablet-based option.

Hobbyists use Fix Zole to help manage internal parasites and intestinal protozoan flagellates such as Hexamita and Spironucleus.

These problems can appear through feeding changes, unusual droppings, weight loss, behavioral changes, or visible physical signs in certain freshwater fish.

Metronidazole works against certain protozoa and anaerobic organisms. When used as directed, it can form part of a broader care plan that includes stable water quality, reduced stress, and appropriate nutrition.

It is not intended for ich or flukes, and it is not normally the first choice for typical fin rot unless the underlying cause has been confirmed by an aquatic professional.

Fix Zole from Aqua Soma Labs delivers 250 mg or 500 mg of metronidazole per tablet in 60-count bottles with fresh expiration dates.

Choose the tablet strength that matches your treatment-tank volume and treatment plan. Tablets may be pre-dissolved in a small cup of aquarium water before being added evenly to the treatment tank.

Use Fix Zole when fish or pet birds show signs that may be associated with protozoan flagellates or anaerobic-sensitive problems.

Fish-Specific Symptoms

  • Loss of appetite or gradual weight loss
  • White, stringy droppings
  • Hole-in-the-head lesions or pits along the head and lateral line
  • Malawi bloat or cichlid bloat
  • Swollen abdomen
  • Faded color, darkening, or body discoloration
  • Lethargy, hiding, or reduced activity
  • Sudden decline in cichlids or discus associated with Hexamita or Spironucleus

Bird-Specific Symptoms Under Avian Veterinary Guidance

  • Yellow plaques in the throat or crop
  • Canker or trichomonosis
  • Pigeon canker, especially in racing pigeons
  • Frounce in falcons, hawks, owls, and other raptors
  • Loose or watery droppings possibly associated with giardia
  • Reduced appetite or weight loss
  • Difficulty swallowing or visible discomfort while eating
  • Fluffed-up feathers or lethargy

Supporting treatment with clean water, stable temperature, low stress, and appropriate husbandry helps reduce setbacks and improve outcomes.

For pet birds, always confirm the diagnosis with an avian veterinarian before administering metronidazole.

Order online: Fix Zole ships from our United States warehouse the same business day according to the current order-processing schedule.

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.

Fish Zole vs Fix Zole: What Changed?

If you previously used Thomas Labs Fish Zole, Fish Zole Forte, or Aqua-Zole by Aqua Soma Labs, here is what you need to know about Fix Zole.

Active ingredient

Same as Fish Zole, Fish Zole Forte, and Aqua-Zole

Fix Zole uses the same metronidazole that hobbyists relied on under the Thomas Labs Fish Zole, Fish Zole Forte, and Aqua Soma Labs Aqua-Zole names.

Manufacturer

New Fix Product Line

Fix Zole is produced by Aqua Soma Labs, which now manufactures the Fix line after Thomas Labs discontinued its Fish Zole products.

Bottle count

Same 60-Count Bottles

Each bottle contains 60 tablets. Choose between the 250 mg and 500 mg strengths according to the treatment-tank size and plan.

Presentation

Updated Packaging, Same Formula

The brand name, bottle design, and label have changed, while the metronidazole tablet strengths remain familiar.

Benefits of Fix Zole for Fish & Birds

01

Targeted Protozoan Support

Commonly used to help manage internal parasites and protozoan flagellates such as Hexamita and Spironucleus, which may be associated with appetite loss, weight loss, white stringy droppings, Malawi bloat, and hole-in-the-head symptoms.

02

Stocked and Ready to Ship

Fix Zole ships from a United States warehouse according to the current processing schedule, helping aquarium keepers obtain treatment quickly when concerning signs appear.

03

Avian Vet-Guided Option

In non-food pet birds, metronidazole may be used under avian veterinary guidance for specific protozoal concerns such as giardia, frounce, and pigeon canker caused by trichomonosis.

04

Flexible 250 mg or 500 mg Tablets

Choose the strength that fits your treatment setup. A consistent amount per tablet helps aquarium keepers scale treatment across different tank volumes.

05

Ideal for Hospital Tanks and Quarantine

A separate hospital tank makes observation and dosing easier while helping protect the display aquarium's biological filter and sensitive tank mates.

06

Fits a Complete Care Plan

Treatment works best when combined with stable temperature, clean water, appropriate feeding, good aeration, and reduced environmental stress.

07

Targeted, Not a One-Size-Fits-All Remedy

Fix Zole is not normally used for ich, gill flukes, Costia, fungus, or ordinary fin rot unless the cause has been professionally identified.

Usage Guidelines & Instructions

Directions for Use:
1

Set Up a Separate Treatment Area

Move affected fish to a dedicated hospital or quarantine tank whenever possible.

This allows you to monitor behavior, control dosing more precisely, and reduce unnecessary exposure in the main display aquarium.

2

Directions for Fish Aquariums

Pre-dissolve the tablet in a small cup of aquarium water, then distribute the prepared solution evenly across the treatment tank.

250 mg strength: Add one 250 mg tablet per 10 gallons or 38 litres of treatment water.

500 mg strength: Add one 500 mg tablet per 20 gallons or 76 litres of treatment water.

Repeat the dose every 24 hours and perform a partial water change between treatments.

3

Adjust the Filtration

Remove activated carbon and other chemical filtration media during treatment.

Keep strong aeration running because activated carbon can reduce the amount of metronidazole available in the treatment water.

4

Continue Treatment and Monitor Results

Continue daily treatment for 5 to 10 days and do not exceed 10 days unless specifically directed by a qualified aquatic veterinarian.

If there is no improvement within five days, discontinue treatment and consult an aquatic professional.

5

Use in Pet Birds Under Veterinary Guidance

Administer metronidazole to non-food pet birds only under the direction of an avian veterinarian.

The veterinarian should confirm the diagnosis and determine the amount, frequency, and duration based on the bird's species, weight, and condition.

Tablets may be given whole, divided, or crushed into soft food only as specifically instructed.

Fix Zole Amounts by Aquarium Size

Tank volume Metronidazole per use 250 mg tablets 500 mg tablets
10 gallons (38 L) 250 mg 1 tablet Not applicable
20 gallons (76 L) 500 mg 2 tablets 1 tablet
30 gallons (114 L) 750 mg 3 tablets 1 tablet plus one 250 mg tablet
40 gallons (151 L) 1,000 mg 4 tablets 2 tablets
55 gallons (208 L) Approximately 1,375 mg 5 to 6 tablets Approximately 3 tablets
These figures follow the label-style guideline of 250 mg per 10 gallons, approximately 25 mg per gallon. Dose according to the water volume of the treatment tank, not the number of fish. The current bottle label or your aquatic veterinarian's instructions take priority over this quick-reference chart.

What to Expect During Treatment

Days 1 to 2

Fish may hide or eat less while treatment begins. Maintain the schedule and keep aeration strong.

Days 3 to 5

Look for improving appetite, more normal droppings, and steadier activity. Stop and seek professional advice if the fish worsen or no change is seen by day five.

Days 5 to 10

Complete the recommended treatment period even when improvement appears. After treatment, perform a partial water change and restore activated carbon.

What You Need Before You Start

Prepare the following supplies before administering the first treatment:

  • A separate hospital or quarantine tank
  • A suitable heater
  • An air stone or established sponge filter
  • An ammonia and nitrite test kit
  • Aquarium dechlorinator
  • A small net for gentle transfer
  • A clean cup for pre-dissolving each tablet

Pro Tip: After treatment, perform a partial water change and reintroduce activated carbon, if normally used, to help clear remaining treatment from the aquarium water.

How Fix Zole Works

Fix Zole uses metronidazole, an ingredient aquarium keepers have relied on for years for certain protozoan and anaerobic-sensitive problems.

In practical terms, metronidazole works against specific protozoa and anaerobic organisms, giving affected fish a better opportunity to recover when the underlying condition is susceptible to it.

This is why aquarium keepers use it when they suspect intestinal flagellates such as Hexamita and Spironucleus rather than for ich, flukes, fungal problems, or typical fin rot.

Each tablet also contains standard inactive ingredients that help hold the tablet together, support storage stability, and allow the tablet to disperse when mixed with water.

The exact inactive ingredient list may vary by batch and may not always be publicly listed.

Safety and Tank Notes

When used as directed, Fix Zole usually causes no problems in ornamental aquarium fish and non-food pet birds.

Incorrect amounts, extended treatment, unnecessary repeat treatments, or combining multiple products can increase stress and the risk of unwanted effects.

Fish

Possible reactions include temporarily reduced appetite, mild lethargy, or hiding behavior.

If severe distress develops, including rapid gill movement, loss of balance, surface gasping, or lying on the bottom, stop treatment, increase aeration, perform a partial water change, and seek aquatic veterinary advice.

Birds

Use metronidazole only under avian veterinary guidance.

Possible reactions may include reduced appetite, loose or changed droppings, and lethargy, particularly if the bird is sensitive or the administered amount is incorrect.

If the bird becomes fluffed up, inactive, or stops eating, discontinue use and contact an avian veterinarian.

Invertebrates

Sensitivity can vary between shrimp, snails, corals, and other invertebrates.

Whenever possible, treat fish in a separate hospital tank rather than dosing a display aquarium containing sensitive invertebrates.

Safe Use in Your System

Do not combine Fix Zole with other treatments unless advised by a qualified professional.

Avoid routine preventative use. If symptoms persist or return, confirm the diagnosis before repeating treatment.

Storage & Handling

Store Fix Zole at a controlled room temperature of 59โ€“86ยฐF or 15โ€“30ยฐC in a cool, dry place.

Keep the container tightly closed to protect the tablets from moisture and light.

Keep out of reach of children and pets.

Important Safety Warning: Fix Zole is intended for ornamental aquarium fish and non-food pet birds only. It is not for animals raised for food. Always follow current label directions.

Shipping & Returns

Shipping Policy

Orders ship from our United States warehouse within one business day through USPS or UPS.

Shipping rates and estimated delivery times are calculated at checkout.

Review Shipping Policy โ†’

Refund Policy

If there is an issue with your order, eligible items may be returned or exchanged within 30 days according to the current store guidelines.

Review the refund policy before sending any product back.

Review Refund Policy โ†’

Frequently Asked Questions

What is Fix Zole used for in aquarium fish and pet birds?

Fix Zole contains metronidazole and is used for certain protozoan and anaerobic-sensitive problems in ornamental fish. These may include Hexamita, Spironucleus, white stringy droppings, internal flagellates, Malawi bloat, and hole-in-the-head symptoms.

Use in non-food pet birds should occur only under avian veterinary guidance.

What is in Fix Zole?

Each tablet contains either 250 mg or 500 mg of metronidazole. Both strengths are supplied in 60-count bottles.

What does metronidazole treat in fish?

Metronidazole is generally used against certain internal protozoa, intestinal flagellates, and anaerobic organisms. It is commonly associated with treatment plans for Hexamita and Spironucleus in susceptible ornamental fish.

Is Fix Zole the same as Fish Zole or Fish Zole Forte?

Fix Zole is presented as the current Aqua Soma Labs replacement for the discontinued Fish Zole and Fish Zole Forte products. The familiar 250 mg and 500 mg metronidazole tablet strengths remain available.

Is Fix Zole the same as Aqua-Zole by Aqua Soma Labs?

Fix Zole is the updated Fix-brand version of the metronidazole tablets previously sold under names such as Aqua-Zole.

Will Fix Zole harm my tank's biological filter?

Treatment may disturb aquarium balance, particularly when used in a display aquarium. A separate hospital tank is preferred, and ammonia and nitrite should be monitored throughout treatment.

How do I choose between 250 mg and 500 mg tablets?

Choose the strength according to the treatment-tank volume. The supplied guide uses one 250 mg tablet per 10 gallons or one 500 mg tablet per 20 gallons.

Can I give Fix Zole to my dog or cat?

No. This product is labeled for ornamental aquarium fish and non-food pet birds. It is not intended for dogs, cats, humans, or food-producing animals.

Does metronidazole help with hole-in-the-head symptoms?

Aquarium keepers commonly use metronidazole when hole-in-the-head symptoms are suspected to involve intestinal flagellates such as Hexamita or Spironucleus. Similar lesions may have other causes, so diagnosis is important.

Will Fix Zole treat ich or gill flukes?

Fix Zole is not normally used for ich, white spot disease, or gill flukes. Those conditions generally require different treatment approaches.

Can Fix Zole treat fin rot or other bacterial infections?

Fix Zole is not normally the first choice for typical fin rot. It is more commonly used for certain protozoan flagellates and anaerobic-sensitive problems.

Can I use Fix Zole as routine prevention?

Routine preventative use is not recommended. Treatment should be based on observed symptoms, the product label, and professional guidance when the diagnosis is uncertain.

How long should I treat with Fix Zole?

The supplied directions describe treatment every 24 hours for 5 to 10 days, without exceeding 10 days. Follow the current bottle label and discontinue if no improvement is seen within five days.

How much metronidazole do I use per gallon?

The supplied reference is 250 mg per 10 gallons, approximately 25 mg per gallon. Pre-dissolve the tablet in aquarium water and dose according to the actual water volume of the treatment tank.

Is Fix Zole safe in saltwater tanks?

Fix Zole is presented for freshwater and saltwater treatment tanks. A separate hospital tank is recommended, especially when the display aquarium contains corals or other invertebrates.

Is Fix Zole reef-safe or safe with shrimp and snails?

Sensitivity varies by species. Treat fish separately whenever possible rather than exposing shrimp, snails, corals, and other invertebrates.

Can I combine Fix Zole with other treatments?

Do not combine treatments unless a veterinarian or qualified aquatic professional specifically recommends the combination.

How do I administer metronidazole to pet birds?

Administer metronidazole to non-food pet birds only under avian veterinary direction. The veterinarian must determine the amount, administration method, frequency, and duration.

How soon should I see improvement with Fix Zole?

Some improvement may become visible within three to five days through increased appetite, more normal droppings, and improved activity. Stop and seek professional advice if the animal worsens or no improvement is seen within five days.

Where can I buy metronidazole for fish online?

Fix Zole 250 mg and 500 mg tablets can be ordered through this online store and shipped according to the current United States warehouse processing and shipping policy.

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Verification snapshot: This page is written from the current product label for this item and reviewed for accuracy and consistency before publishing.

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Directions, treatment duration, storage, and warnings are taken from the current product label for this item.

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Last reviewed: July 10, 2026