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Fish Mox (Amoxicillin)

By | Last Updated: 22nd February 2023

What is Fish Mox (Fish Amoxicillin)

Fish Mox and Fish Mox Forte are broad-spectrum antibiotics effective against a wide range of gram-positive and gram-negative bacteria in both saltwater and freshwater aquarium fishes. It helps in controlling eye infections, skin ulcerations, pop-eye, columnaris disease, red pest, tail or fin rot, dropsy, and gill disease [1, 2].

How does Fish Amoxicillin work

It is a type of penicillin that targets disease-causing bacteria and halts their growth by keeping them from developing cell walls. Thus the medication stops the bacteria from reproducing and finally gets rid of the infection [3].

Quick Information

Fish Mox

Generic name: Amoxicillin

Type: Penicillin group of antibiotic [3]

Brand names: Fish Mox®, Fish Mox Forte® [1, 2]

Manufacturer: Thomas Labs [2]

Active ingredient: Amoxicillin Trihydrate [2]

FDA Approved: No [5]

Availability: Non-prescription medication sold over the counter [4]

Who can take it: Aquarium or ornamental fish [2]

Form: 250mg and 500mg capsules, powder [1, 2]

Fish Mox (Amoxicillin) safe dosage

Always consult with your vet before using Fish Mox for treating your pet fishes. Follow the dosage instructions given by the veterinarian or read the directions on the drug label carefully.

The commonly recommended dosage is one 250 mg capsule per 10 gallons of aquarium water or a 500 mg capsule for every 20 gallons of fish tank water. Repeat treatment in 24 hours [1, 2].

How to use Fish Mox

Add the prescribed amount of medication to your aquarium and repeat after 24 hours. Perform partial water changes between treatments. Depending on the severity of the bacterial infection, the vet may suggest you to continue giving the medicated bath for 5-10 days. However, it is usually recommended to stop the treatment if the symptoms do not improve within 5 days. Changing about 20% of the tank water and using a charcoal filter may help in removing the yellow color caused by the addition of the medication [5].

Can humans take Fish Mox and Fish Mox Forte

Fish Mox and Fish Mox Forte are meant for use in aquarium fish only and have not been approved by the FDA for humans [5]. However, some people still use these medications for lessening the symptoms of sinus, sore throats, bronchitis, gonorrhea, UTI, tooth, ear, and kidney infections.

Is it safe to use

Although the primary ingredient is the same as in antibiotics taken by humans, they possibly contain liquids or flakes that could be harmful to people. Moreover, they might react with any medication you are already taking [6]. If you are allergic to penicillin, you may experience side effects like chest tightness, extreme itchiness, skin rash, sore throat, swelling of the face, difficulty breathing, vomiting, and upset stomach [3].

Keep out of reach of children, and store in a dry place at room temperature [1, 5].

Do not give these medications to fishes that are meant to be used for food [5].

Is it safe for dogs and cats

It is often given to cats and dogs as well for treating bacterial infections. There is a lack of evidence regarding its safety. So, always be sure not to administer Fish Mox and Fish Mox Forte to your pet dog and cat without first talking to a vet.


    1. Fish-Mox Forte 500 Mg 100 Count – Walmart.com
    2. Aquarium Fish: The ‘Eyes’ Have it: A Review of Eye Health in Aquarium Fishes – Reefs.com
    3. Amoxicillin: What is it and how does it work – Medicalnewstoday.com
    4. About Fish Antibiotics – Fishmoxfishflex.com
    5. Fish Mox Forte – amoxicillin capsule – Dailymed.nlm.nih.gov
    6. Humans are ingesting fish antibiotics to treat their own illnesses – News5cleveland.com

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