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Metronidazole (updated 7-5-22)
What It Treats – Internal parasites (flagellates), Brooklynella, Uronema marinum**
How To Treat – It is best to use pharmaceutical-grade Metronidazole powder (sold here). Dosage is 25 mg/gal every 48 hours (or 24 hours for severe problems) with a 25% water change before each treatment. Treat for 10-14 days.
Metro is the active ingredient found in Seachem MetroPlex, and also API General Cure & Fritz ParaCleanse. (General Cure and Paracleanse also contain Praziquantel.)
For Brook, dose metro directly into a quarantine tank every 48 hours for 10-14 days. For Uronema**, dose metro directly into a quarantine tank every 24 hours for at least 2 weeks. For internal parasites, it is best to soak metro in the fish’s food. Use Seachem Focus to bind it to the food, and feed daily for 3-4 weeks or until symptoms disappear. My recipe for food soaking metro (and prazi) can be found below:
1 tbsp food (preferably frozen food or pellets)
1 scoop (~ 1/8 teaspoon) of medication
1 scoop Seachem Focus (this makes it reef safe)
A pinch of Epsom salt to help expel dead worms/parasites
A few drops of saltwater or fish vitamins
Stir until a medicated food slurry has been achieved
Feed after soaking for 30 mins
Refrigerate or freeze any leftovers for future use
Whether or not metro is “reef safe” is a topic for debate. The general consensus is that while soaking it in fish food IS “reef safe,” dosing it directly into the water column IS NOT and should only be done in quarantine.
Pros – Can be soaked in fish food, making it reef safe. However, Seachem Focus needs to be used to prevent the medication from leaching out. Also, it is a good idea to run carbon just in a case.
Cons/Side Effects – Certain fish seem to have a negative reaction to metronidazole; however this is rare.
** Uronema is usually only treatable externally before red sores show up. If the parasites have made their way to the dermis of a fish, or if a fish is infected with Uronema internally (intracellularly), there are no known treatments for these scenarios.
What It Treats – Internal parasites (flagellates), Brooklynella, Uronema marinum**
How To Treat – It is best to use pharmaceutical-grade Metronidazole powder (sold here). Dosage is 25 mg/gal every 48 hours (or 24 hours for severe problems) with a 25% water change before each treatment. Treat for 10-14 days.
Metro is the active ingredient found in Seachem MetroPlex, and also API General Cure & Fritz ParaCleanse. (General Cure and Paracleanse also contain Praziquantel.)
For Brook, dose metro directly into a quarantine tank every 48 hours for 10-14 days. For Uronema**, dose metro directly into a quarantine tank every 24 hours for at least 2 weeks. For internal parasites, it is best to soak metro in the fish’s food. Use Seachem Focus to bind it to the food, and feed daily for 3-4 weeks or until symptoms disappear. My recipe for food soaking metro (and prazi) can be found below:
1 tbsp food (preferably frozen food or pellets)
1 scoop (~ 1/8 teaspoon) of medication
1 scoop Seachem Focus (this makes it reef safe)
A pinch of Epsom salt to help expel dead worms/parasites
A few drops of saltwater or fish vitamins
Stir until a medicated food slurry has been achieved
Feed after soaking for 30 mins
Refrigerate or freeze any leftovers for future use
Whether or not metro is “reef safe” is a topic for debate. The general consensus is that while soaking it in fish food IS “reef safe,” dosing it directly into the water column IS NOT and should only be done in quarantine.
Pros – Can be soaked in fish food, making it reef safe. However, Seachem Focus needs to be used to prevent the medication from leaching out. Also, it is a good idea to run carbon just in a case.

Cons/Side Effects – Certain fish seem to have a negative reaction to metronidazole; however this is rare.
** Uronema is usually only treatable externally before red sores show up. If the parasites have made their way to the dermis of a fish, or if a fish is infected with Uronema internally (intracellularly), there are no known treatments for these scenarios.
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