Mafiaman brings up an interesting point. Up until now, I'd never heard of metronidazole being used for ich. I did some digging online and found very little information about it, other than it being a suggested second line treatment, and the statement on the box that it's "safe for biological sand beds
Having used it clinically to treat anaerobic infections in humans, I'm skeptical to say the least. (About the "safe for sand bed" part.) While Clostridium sp. does vary from the Nitrosomonas/Nitrobacters, I'd like to hear some results before recommending it. Just wondering, as the exact mechanism of action for the drug is unknown, as far as I could find.
Mafiaman - have you used it sucessfully in a reef? I'm really curious about this.