Why is using charcoal a bad idea? Will it kill the plants?I3u11he4d said:I use a fluval 304 on my 55 gal. w/ ceramic rings and 200 grams of purigen.Canisters seem to be the way to go on a planted tank just dont use any charcoal,this is a bad idea .If your stocking levels are low you may not even need a filter,so whats in the tank?