how to use metronidazole for fish (for treating anaerobic bacteria) and anti-protozoal medication where to buy metronidazole for fish you can buy metronidazole for koi fish at petstore near you or drug stores. metronidazole for fish dosage Directions from SeaChem Metronidazole; use 100 mg. for every 10 gallons (40 L). Repeat every 2 days until symptoms […]