as soon as a hogaboom started to get a little hole in the head I bought the little bottle of metro powder and started treatment. I didn't have a q-tank so I treated the whole tank . he started to look better right away, but since I treated the whole tank it was going to be expensive so I got(I believe it was tetra parasite guard) or one of those $5.00 petsmart box medications that had metro in it to finish of the treatment . it worked great. I probably could have used the 5 dollar meds for the whole thing but live and learn