Amoxicillin for Fish (Fish Mox)
Quick answerAmoxicillin is a beta-lactam antibiotic that kills bacteria by blocking construction of their cell walls. It is one of the most commonly used antibiotics in the aquarium hobby. Mainly gram-positive bacteria, plus some gram-negative species. It is not active against parasites, viruses or fungi.
What amoxicillin is commonly used for
- Fin rot and tail rot
- Bacterial ulcers and body wounds
- Mouth and skin infections
- Secondary infections after injury or handling
Things to know
- Beta-lactams can be broken down by some resistant bacteria; if a fish does not improve, a different class is usually the next step.
- People with a penicillin allergy should avoid handling the capsules or treated water without gloves.
- Antibiotics can harm the beneficial bacteria in a biofilter, so treating in a hospital tank protects the main aquarium.
How it compares with other options
Amoxicillin is one of several classes of antibiotic used by keepers. Our comparison guide lays out which class suits which problem, and our treatment packs combine complementary classes so you have a backup ready.
Products containing amoxicillin
Amoxicillin FAQ
What is amoxicillin used for in fish?
Aquarists commonly use amoxicillin for bacterial problems such as fin rot, ulcers and skin infections. It only works on bacteria, so it will not help with parasites like ich or with true fungal infections.
Is Fish Mox the same as human amoxicillin?
Fish Mox contains the same active ingredient, amoxicillin, but it is labeled and sold for ornamental aquarium fish only. It is not intended for human use or for fish raised for food.
Should I use 250mg or 500mg capsules?
The strength is a packaging choice. Larger systems use more medication, so many keepers pick the 500mg size to reduce the number of capsules to handle. Always follow the directions printed on the product you receive.
Responsible use. For ornamental aquarium fish only. Not for human use or fish intended for food. Follow the label and consult a veterinarian when unsure.