Metro is only suitable for eliminating Uronema from the water + tank surfaces. A fish infected with Uronema should be treated with formalin, or possibly Chloroquine phosphate. However, once red sores show up, or if a fish is infected with Uronema internally (intracellularly), the fish is generally considered to be untreatable. There are only a few anecdotal accounts of fish with red sores being successfully treated by using tea tree oil (Melafix).

How To Treat: It is best to use pharmaceutical-grade Metronidazole powder (sold here). Dosage is 25 mg/gal every 48 hours (or every 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. (Please note: General Cure and Paracleanse also contain Praziquantel.)

For Brook, dose metro directly into a quarantine tank every 48 hours for 10-14 days. For internal parasites, you have two options: (1) Dose the water every 48 hours for 2 weeks and hope the fish drinks enough of the medicated water to be effective. (2) Soak metro in the fish’s food. For the latter, I recommend using Seachem Focus** to bind the medication to the food. Feed daily for 2-4 weeks or until symptoms disappear. My recipe*** for food soaking metro can be found below:

1 tbsp food (preferably frozen food or pellets)
1 scoop (~ 1/8 teaspoon) of medication
1 scoop Seachem Focus (binder)
A pinch of Epsom salt to help expel dead worms/parasites

Several drops of saltwater or fish vitamins to wet everything down
Stir until a medicated food slurry has been achieved
Feed after soaking for 30 mins

Refrigerate or freeze any leftovers for future use

** Agar or unflavored gelatin can be used in lieu of Focus. More medicated food recipes can be found here: How To Make Medicated Feed

Whether or not metro is “reef safe” is a topic for debate. I personally feel that soaking it in fish food is an acceptable risk; whereas dosing it directly into the water column IS NOT and should only be done in quarantine (or a FOWLR).

Pros: Metro is generally well tolerated by most species, and 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: It is rare, but every now & then I run across a particular fish that seems to have a negative reaction to metronidazole.

*** The “proper way” to food soak medications is by weight. (Some sources say to weigh the food, some even say to weigh the fish. :eek:) I find this to be impractical for the casual hobbyist, and that my “shotgun approach” to food soaking medications generally works. However, for those who wish to food soak Metronidazole properly it should be dosed in food at 0.50% by weight. There are oral dosages listed here (Table 1) for other medications: CIR 84/FA084: Use of Antibiotics in Ornamental Fish Aquaculture