Not necessary, and it's not a good idea to add more chems than necessary to your water. Basically it works by binding together tiny particles into clumps so your water looks more clear. It removes nothing. Some people claim some types of clarifiers can put a coating/glob over your fish's gills and cause breathing issues, but I don't know about that one. It contains an aluminum ingredient found in antispirspirants and cosmetics + DI Water :S Essentially, it's a product designed to try to get people to add chems which make the water look clear/clean instead of doing correct water changes to actually make the water clean. There is no substitution for water changes.
Last edited by callistra; 01-19-2013 at 12:34 PM.