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Fish Amoxicillin (Fish Mox) 250mg 30 Count Bottle - Aquarium Antibacterial for Dropsy and Bacterial Dropsy
Fish Mox (Amoxicillin) 250mg 100 Count - Broad Spectrum Fish Treatment for Fin and Tail Rot
Fish Mox (Amoxicillin) 500mg 30 Count - Potent Fish Antibacterial for Red Pest and Ulcers
Fish Mox (Amoxicillin) 500mg 100 Count - Freshwater and Saltwater Fish Antibacterial
Fish Amoxicillin (Fish Mox) 250mg 30 Count Bottle - Aquarium Antibacterial for Dropsy and Bacterial Dropsy
Fish Mox (Amoxicillin) 250mg 100 Count - Broad Spectrum Fish Treatment for Fin and Tail Rot
Fish Mox (Amoxicillin) 500mg 30 Count - Potent Fish Antibacterial for Red Pest and Ulcers
Fish Mox (Amoxicillin) 500mg 100 Count - Freshwater and Saltwater Fish Antibacterial

Fish Mox (Fix Mox) 250mg/500mg 30/100ct

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Fix Mox (Fish Mox) Amoxicillin Capsules for Ornamental Fish & Pet Birds, 250 mg / 500 mg

Fix Mox at a Glance
For Ornamental aquarium fish and non-food pet birds
Helps with Fin and tail rot, dropsy, columnaris, red streaks, skin ulcers
Form Capsules, 250 mg or 500 mg each
Count Sizes 30 count, 100 count
Water Type Freshwater and saltwater aquariums
Made In United States by Aqua Soma Labs

Fix Mox (Fish Mox) is a fish amoxicillin treatment in 250 mg and 500 mg capsules for ornamental aquarium fish and non-food pet birds. In freshwater and saltwater tanks it is used for common bacterial problems: dropsy (body swelling), fin and tail rot, columnaris, hemorrhagic septicemia, red streaks, gill disease, swim bladder infections, abscesses, and skin ulcers. With an avian veterinarian's guidance, the same capsules can be part of an amoxicillin plan for problems such as crop infections and salmonella or paratyphoid in pigeons and other pet birds.

Fix Mox gives you a 250 mg or 500 mg strength, so you can match it to the job: a small hospital tank, a larger community aquarium, or, with veterinary input, a loft or aviary. It is the current replacement for the discontinued Thomas Labs Fish Mox (fishmox). The 250 mg option stands in for the original strength, and the 500 mg option, the fish amoxicillin 500mg strength, covers what aquarists knew as Fish Mox Forte and Aqua Mox. Stock ships from our United States warehouse with fresh expiration dates and clearly printed strengths.

Start treatment early, at the first signs of bacterial stress. Those signs differ between fish and birds, so use the lists below to know what to watch for.

Fish-Specific Symptoms

  • Fin and tail rot (frayed or rotting fins)
  • Dropsy (body swelling)
  • Pop-eye (bulging eyes)
  • Red streaks or open sores on the body
  • Skin ulcers and abscesses
  • Columnaris and gill disease
  • Lethargy, rapid breathing, loss of appetite

Bird-Specific Symptoms (Under Veterinary Guidance)

  • Crop infections
  • Suspected salmonella / paratyphoid
  • Fluffed-up feathers, lethargy or inactivity
  • Decreased appetite
  • Loose or changed droppings
  • Labored or difficult breathing

For birds, only use Fix Mox when an avian veterinarian has recommended amoxicillin for a specific problem. Catching an infection early, paired with clean water and good housing, gives your fish and birds the best chance to recover.

Order online and enjoy same-day dispatch on orders placed before 1:30 p.m. CT, Monday through Friday. Fix Mox ships directly from our United States warehouse via USPS or UPS.

Important Notice: This product is intended for aquarium and ornamental fish and pet birds only. It is not for animals used for food.

Fish Mox vs Fix Mox: What Changed?

If you used to buy Fish Mox, Fish Mox Forte, or Aqua Mox, those brands are now discontinued or hard to find. Fix Mox from Aqua Soma Labs uses the same amoxicillin at the same strengths and steps in as a direct replacement for aquarium use.

Same Amoxicillin Inside
Fish Mox and Fix Mox both contain amoxicillin (250 mg or 500 mg per capsule), what aquarists have relied on for years.

Updated Labeling & Packaging
Fix Mox carries clear, modern labeling, with usage guidance, the amoxicillin strength, and storage notes printed on the bottle.

Same Capsule Format
Pull-apart capsules that dissolve in tank water, matching the format aquarists knew from Thomas Labs Fish Mox or Aqua Mox.

Fresh Stock & Current Expiration Dates
Every bottle ships with recent production and clearly printed expiration dates.

Benefits of Fix Mox for Fish & Birds

  • Covers Common Fish Infections

    As an aquarium treatment, amoxicillin is used against many of the bacteria behind dropsy, fin and tail rot, red streaks, gill disease, swim bladder infections, and skin ulcers, in both freshwater and saltwater tanks.

  • Handles External and Internal Problems

    Use it for outward signs like frayed fins, open sores, or red patches, and for internal infections such as hemorrhagic septicemia that bring swelling, lethargy, or loss of appetite. Treat affected fish in a hospital tank.

  • Flexible 250 mg and 500 mg Strengths

    Amoxicillin in a 500 mg or 250 mg capsule lets you scale from a small quarantine tank to a large system. A common guide is 250 mg per 10 gallons or 500 mg per 20 gallons, and an aquatic veterinarian can tailor it.

  • Keep a Bottle on Hand

    Bacterial problems move fast, so it helps to have Fix Mox ready before trouble starts. Keeping a bottle on the shelf, stored cool and dry, means you can begin treatment at the first sign of infection in your aquarium.

  • Easy to Prepare for Fish and Vet-Directed Birds

    The capsules pull apart, and the contents dissolve fast in tank water so the treatment reaches even shy or hiding fish. Under avian veterinary guidance, the same contents mix into soft food or water for birds with problems like crop infections.

  • Built for Hospital and Quarantine Tanks

    Fix Mox does its best work in a separate hospital or quarantine tank. There you can pull carbon and UV, hold water quality steady, and watch the sick fish without treating healthy tank mates or sensitive invertebrates.

  • A Modern Swap for Discontinued Brands

    When the old Thomas Labs Fish Mox or Aqua Mox is unavailable, Fix Mox is the go-to replacement. Clear strength labels and fresh stock make it easy to match the dose to your tank or a vet-directed bird plan.

Usage Guidelines & Instructions

Directions for Use:

  1. Set Up a Separate Treatment Area

    Move sick fish to a dedicated hospital or quarantine tank before you dose. Take out the activated carbon and switch off UV sterilizers, since both pull amoxicillin from the water. A 20-25% water change before the first dose lowers stress and starts treatment on cleaner water.

  2. Directions for Fish Aquariums

    Follow the label guide of 250 mg amoxicillin per 10 gallons (38 L) or 500 mg per 20 gallons (76 L). Open the capsule, stir the powder into a cup of tank water, then pour it evenly around the treatment tank. Repeat every 24 hours for 5-10 days, with a partial water change between doses. If nothing improves after about 5 days, or fish look worse, stop and ask an aquatic veterinarian.

  3. Use in Pet Birds (Under Veterinary Guidance)

    Use Fix Mox in pigeons and other non-food pet birds only when an avian veterinarian directs it. The vet sets the correct amount for the bird's weight, how often to give it, and how long to continue. Capsules are usually opened into soft food or drinking water so the bird takes the full amount, but follow the vet's exact instructions rather than guessing.

  4. Maintain Water Quality and Finish the Treatment

    Through treatment, keep an eye on ammonia, nitrite, and temperature, and keep aeration strong. Finish the full treatment unless a veterinarian says otherwise; stopping early lets symptoms come back. Afterward, run a partial water change and put activated carbon back in to clear out any leftover amoxicillin and help the tank settle.

Fix Mox Amounts by Aquarium Size
Tank volume Amoxicillin per use 250 mg capsules 500 mg capsules
10 gallons (38 L) 250 mg 1 n/a
20 gallons (76 L) 500 mg 2 1
30 gallons (114 L) 750 mg 3 1 + one 250 mg
40 gallons (151 L) 1000 mg 4 2
55 gallons (208 L) about 1375 mg 5 to 6 3

These figures come from the label-style guideline of 250 mg per 10 gallons, roughly 25 mg per gallon. Dose by the water volume of your treatment tank, not by the number of fish, give one dose every 24 hours for 5 to 10 days, and round to the nearest practical capsule. The bottle label or your aquatic veterinarian takes priority over this quick-reference chart.

What to Expect During Treatment

Days 1 to 2

Fish may hide or eat less, and the water can look slightly cloudy. This is normal early on. Keep dosing on schedule and keep aeration strong.

Days 3 to 5

Look for signs it is working: sores and red patches stop spreading, appetite starts to return, and breathing steadies. If there is no change by day 5, or the fish look worse, stop and ask an aquatic veterinarian.

Days 5 to 10

Even if the fish are improving, finish the full treatment so the infection does not return. Afterward, run a partial water change and put activated carbon back in to clear any leftover amoxicillin.

What You Need for Treatment

A little setup before the first dose saves trouble later.

  • A separate hospital or quarantine tank, so you are not treating the whole display.
  • A heater and an air stone or sponge filter for steady temperature and strong aeration.
  • An ammonia and nitrite test kit to keep tabs on water quality.
  • A dechlorinator for the water changes between doses.
  • A small net and a clean cup for gentle transfer and measuring the dose.

Pro Tip: Treat sick fish in a separate hospital tank rather than the main display whenever you can. It keeps your display biofilter and invertebrates safe while you focus the treatment where it is needed.

How Fix Mox Works

Each Fix Mox capsule contains amoxicillin trihydrate, 250 mg or 500 mg. Amoxicillin is used against many Gram-positive and some Gram-negative bacteria, the kind behind fin and tail rot, skin ulcers, red streaks, and certain gill infections in ornamental fish.

Alongside the amoxicillin, each capsule holds standard ingredients that hold the contents together and help them disperse properly in aquarium water, or in soft food for birds under veterinary guidance.

Safety and Tank Notes

At the right amount, Fix Mox usually causes no problems for fish or pet birds. The risk of side effects climbs with too much product, treatment that runs longer than needed, or treating an already stressed animal, and overuse feeds resistance.

  • Fish

    Amoxicillin can cause short-term hiding, mild water cloudiness, and lower appetite during treatment. If a fish shows real distress, rapid gill movement, loss of balance, gasping at the surface, or lying on the bottom, stop, add clean dechlorinated water for better aeration, and call an aquatic veterinarian.

  • Birds

    Mixed into food or water, amoxicillin may cause reduced appetite, loose or changed droppings, and lethargy, especially at too high an amount or in a sensitive bird. A fluffed-up, inactive bird, or one that struggles to breathe or stops eating, should stop treatment and see an avian veterinarian right away.

  • Invertebrates

    Do not use Fix Mox in display tanks with shrimp, snails, or other invertebrates, since strong treatments can harm them and upset the tank. Move affected fish to a separate hospital or quarantine tank instead.

  • Safe use in your system

    Treat in a hospital or quarantine tank where you can, pull activated carbon and switch off UV during treatment, and keep an eye on ammonia, nitrite, and temperature. Do not combine Fix Mox with other treatments unless a veterinarian advises it.

  • Important safety & storage

    Fix Mox is for aquarium and ornamental fish and non-food pet birds only, and not for animals raised for food. If you are sensitive to penicillins, avoid contact with the capsule contents, wash your hands after handling, and wear gloves if needed. Store the capsules in their original container in a cool, dry place at 59-86°F (15-30°C), out of moisture and sunlight, and out of reach of children and pets, with the lid closed.

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Refund Policy: If there is an issue with your order, you may be able to return or exchange items within 30 days according to our store guidelines. Before sending anything back, please review our refund policy carefully.

Frequently Asked Questions

What is Fix Mox used for in fish and birds?

Fix Mox is amoxicillin in 250 mg and 500 mg capsules, sometimes written as fishmox. Aquarists use it for bacterial problems like dropsy (body swelling), fin and tail rot, red streaks, pop-eye, skin ulcers, and some gill infections. For non-food pet birds, it supports a veterinarian-directed plan for selected bacterial issues.

Is Fix Mox the same as Fish Mox or Aqua Mox?

It is the same idea under a current label. Fish Mox, Fish Mox Forte, and Aqua Mox were earlier amoxicillin products for aquarium use, and Fix Mox carries the same active ingredient for the same problems. Follow the Fix Mox label for the amount and duration.

Is Fix Mox (fish mox) the same as amoxicillin?

The active ingredient is amoxicillin trihydrate, at 250 mg and 500 mg per capsule. What differs is the labeling: Fix Mox is made and sold only for ornamental aquarium fish and non-food pet birds, and not for animals raised for food.

Is Fix Mox the same as fish amoxicillin 500mg?

In the 500 mg option, yes. That capsule holds 500 mg of amoxicillin, the strength often searched for as fish amoxicillin 500mg. The 250 mg option holds 250 mg. Same ingredient, same pull-apart capsule, so you pick the strength that fits your tank size or a vet-directed bird plan.

Where can I buy Fish Mox (amoxicillin) online?

If you are wondering where can I buy fish mox, you can order Fix Mox, the current Fish Mox replacement, directly from Fine Pet Health. Orders leave our U.S. warehouse within one business day by USPS or UPS, with clear labels and current expiration dates.

Browse Fish & Bird Treatments Collection →
Can Fix Mox (Fish Mox) be used for dogs or cats?

No. The label covers ornamental aquarium fish and non-food pet birds only, not dogs, cats, or other mammals. A dog or cat that needs amoxicillin should get a vet-recommended, species-specific product and amount.

What is the difference between Fish Mox and Fish Mox Forte?

It comes down to strength. The original Thomas Labs Fish Mox was 250 mg per capsule, while Fish Mox Forte was 500 mg. Fix Mox covers both: choose the 250mg option, the fish mox 250mg equivalent, for standard strength, or the 500mg option for the Forte equivalent. The ingredient and capsule format are the same either way.

How do I know if my fish might need a fish amoxicillin treatment?

Look for frayed or rotting fins, red or white ulcers, red streaks in the fins or body, bulging eyes (pop-eye), labored breathing, or listless behavior that good water quality does not fix. A fish veterinarian or experienced aquarist can confirm whether the cause is bacterial and whether amoxicillin fits.

Can I use Fix Mox in my main community or reef tank?

Better not. Treat sick fish in a separate hospital or quarantine tank. Amoxicillin is not meant for reef tanks or setups with shrimp, snails, corals, or other invertebrates, where it can harm them or knock back the beneficial filter bacteria.

How much Fix Mox should I use per gallon?

The label guide is 250 mg amoxicillin per 10 gallons (38 L) or 500 mg per 20 gallons (76 L). Open the capsule, mix the powder into a cup of tank water, and spread it around the treatment tank. Repeat every 24 hours for 5-10 days, with a partial water change between doses. Measure the tank volume first.

How long should I treat with Fix Mox?

For fish, most treatments run 5 to 10 days, dosing once every 24 hours at roughly 250 mg per 10 gallons (38 L) or 500 mg per 20 gallons (76 L), or as an aquatic veterinarian advises. For birds, the amount and length come from the avian vet, not from the label.

Does Fix Mox work in saltwater aquariums?

Yes. It is used against certain bacteria in both freshwater and saltwater tanks. Treat in a hospital or quarantine tank where you can, to protect the biofilter and any invertebrates in the display.

Is Fix Mox safe for pet birds, and can I treat more than one bird?

Only under an avian veterinarian's direction. The vet works out the correct amount for the bird's weight and decides whether to treat one bird or a whole loft or flock. Do not guess avian amounts or add capsule contents to shared water on your own.

Will Fix Mox affect beneficial bacteria in my aquarium?

It can, if you dose the main tank. Amoxicillin does not tell good bacteria from bad. A hospital tank, regular ammonia and nitrite checks, and partial water changes during and after treatment keep the biofilter protected.

Can Fix Mox treat fungal, viral or parasitic infections?

No. Amoxicillin targets certain bacteria only. It does nothing for fungi, viruses, or parasites like ich, flukes, or worms, which need different treatments chosen with help from an aquatic or avian veterinarian.

Can I combine Fix Mox with other treatments?

Avoid it unless a veterinarian says otherwise. Stacking treatments can stress fish, shift water chemistry, and hide which product is helping or causing trouble. If another treatment is needed, finish the amoxicillin first.

What is the active ingredient in Fish Mox?

Amoxicillin trihydrate. Each Fix Mox capsule holds 250 mg or 500 mg, the same ingredient used in the old Thomas Labs Fish Mox and Aqua Mox products for ornamental aquarium fish.

How should I store Fix Mox capsules?

Keep the capsules in their original container in a cool, dry spot at 59-86°F (15-30°C), out of moisture and sunlight, and away from children and pets, with the lid closed. Check the expiration date and do not use capsules past it.

What should I do if my fish are not improving on Fix Mox?

Stop after about 5 days if there is no change, or sooner if the fish get worse, then improve water quality and aeration and ask an aquatic veterinarian. No response can mean the cause is not bacterial, the bacteria do not respond to amoxicillin, or the dose or length was off.

What is fish mox?

Fish mox is a common name for amoxicillin sold as an aquarium treatment. Fix Mox is the current version: amoxicillin 500 mg and 250 mg capsules for ornamental fish and non-food pet birds. It is used for bacterial problems like fin rot, dropsy, red streaks, and skin ulcers, not fungi, viruses, or parasites.

More Fish & Bird Treatments

Fix Zole (Metronidazole) 250/500mg A treatment for Hexamita, hole-in-the-head disease, and other protozoa-related problems in ornamental fish. Available in 60-count bottles. Shop Fix Zole

Fix Doxy (Doxycycline) 100mg A treatment for columnaris, respiratory infections, and Mycoplasma in fish and non-food pet birds. Available in 30-count and 60-count tablets. Shop Fix Doxy

Fix Zithro (Azithromycin) 250mg A treatment for fin rot, columnaris, gill disease, and avian respiratory concerns in fish and non-food pet birds. Available in 12-count and 30-count tablets. Shop Fix Zithro

Fix Cin (Clindamycin) 150mg A treatment for gram-positive bacterial problems, including skin and soft-tissue concerns, in ornamental fish. Shop Fix Cin

Fix Sulfa (SMZ/TMP) 960mg A treatment used against a range of bacterial infections in ornamental fish. Shop Fix Sulfa

Fix Pen (Penicillin) 500mg A treatment for gram-positive bacterial problems in ornamental fish and non-food pet birds. Shop Fix Pen

Fix Flex (Cephalexin) 250/500mg A treatment for fin rot, ulcers, and bacterial skin infections in ornamental fish and non-food pet birds. Shop Fix Flex

Fix Flox (Ciprofloxacin) 500mg A treatment for gram-negative bacterial problems, including fin rot, ulcers, columnaris, and septicemia, in ornamental fish and non-food pet birds. Shop Fix Flox

Browse all treatments Explore our complete Fish & Bird Treatments Collection for more Fix line products and related treatments.

Guides and treatment tips Visit the Fish & Bird Treatments Blog for practical usage guides, water-care advice and treatment tips.

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