Metronidazole for Fish (Fish Zole)
Quick answerMetronidazole targets protozoa and anaerobic bacteria. It is one of the main tools hobbyists use against internal flagellates such as Hexamita and Spironucleus. Protozoan parasites and anaerobic bacteria. It is not a general-purpose antibiotic.
What metronidazole is commonly used for
- Internal flagellate infections
- Hole-in-the-head disease in cichlids and discus
- White, stringy waste and appetite loss
- Some cases of bloat
Things to know
- It does not treat external parasites such as ich or velvet; those need a different approach.
- Medicated food is often used because sick fish may refuse it, so many keepers dose the water.
- Treat in a hospital tank.
How it compares with other options
Metronidazole is one of several classes of antiparasitic 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 metronidazole
Metronidazole FAQ
Does metronidazole treat ich?
No. Ich is an external parasite that needs different treatment, such as heat with salt or a copper-based product. Metronidazole targets internal protozoa and anaerobic bacteria.
What are the signs of internal parasites?
Common signs include white or stringy waste, weight loss despite eating, pale color and, in cichlids or discus, pitting on the head.
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.