I just bought a Fluval canister filter for the 55g growout. Previously I was just using undergravel with powerheads. So currently I am using the Fluval 70g capacity canister (which is cool as hell by the way) and undergravel. I guess my question is this: Is this new filter going to cycle and kill my fish? It goes through a sponge first, in the 3 trays ive got a carbon first layer, a carbon / bio second layer, and a bio only 3rd layer. Im hoping since ive also got a well established undergravel system in place that adding this new and much improved canister should only make my water better. But I know bio filters will cycle so im just hoping the established U/G will balance that. Let me know if I am mistaken in my theory and headed towards certain doom for my much loved Cichla!