Fish Antiparasitics
Parasites need parasite-specific treatment. Metronidazole is used for internal protozoa such as Hexamita, while copper-based products are used for external parasites like ich and velvet. Read our guides on ich and velvet and bloat and internal parasites.
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Metronidazole (Fish Zole) · guide
Other treatments
Fritz Coppersafe 16 oz
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Internal vs external parasites
External parasites such as ich and velvet live on the skin and gills and are usually treated with a copper-based product or, for some species, heat and salt. Internal parasites such as Hexamita and Spironucleus live in the gut and are commonly treated with metronidazole. Using the wrong category of treatment wastes time, so identify the signs first: white dots or gold dust point to external parasites, while stringy white waste and weight loss point to internal ones.
Safety notes
- Copper is toxic to snails, shrimp and other invertebrates.
- Follow label directions exactly and test copper levels when required.
- Increase aeration during treatment.
Antiparasitics FAQ
Does metronidazole treat ich?
No. Ich is an external parasite. Metronidazole targets internal protozoa and anaerobic bacteria.
Is copper safe for all fish?
No. Scaleless and sensitive species can be harmed and invertebrates will be killed. Check compatibility on the label.
How long should I treat parasites?
Follow the label for the full duration. Medication reaches only some life stages, so the cycle must be covered completely.