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Amoxicillin/Clavulanate for Fish (Fish Clav)

Penicillin-class antibiotic with a beta-lactamase inhibitor ยท Updated 2026-09-30

Quick answerAdding clavulanate to amoxicillin protects the antibiotic from enzymes (beta-lactamases) that some bacteria produce to defeat it. This widens the range of bacteria the drug can reach. A broader spectrum than amoxicillin alone, covering many beta-lactamase-producing gram-positive and gram-negative bacteria.

What amoxicillin/clavulanate is commonly used for

  • Infections that have not responded to plain amoxicillin
  • Stubborn fin rot and ulcers
  • Mixed bacterial infections

Things to know

  • Like other penicillin-class drugs it is ineffective against parasites and fungi.
  • People with penicillin allergies should wear gloves when handling.
  • Use a hospital tank so the main tank biofilter is not disturbed.

How it compares with other options

Amoxicillin/Clavulanate 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/clavulanate

Amoxicillin/Clavulanate FAQ

What does clavulanate add to amoxicillin?

Clavulanate does not kill bacteria on its own. It blocks the enzyme that many resistant bacteria use to destroy amoxicillin, so the amoxicillin can still work.

When would someone choose Fish Clav over Fish Mox?

Keepers typically consider it when a bacterial infection has not improved on plain amoxicillin, or when they suspect a resistant strain.

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.