Did anyone ever say why not to use them, cuz i had one in my 110 gal. and i never had a problem with fish dying or anything. But thanx for the info i will look into getting a Bio Wheel filter also.I asked about under gravel filters a while back and most people stated not to use them. Either a canister or hang one on the back. Also what kind of lights do you plan on using for "lots of plants"?