I advocate canisters for a reason which most, even fish lovers, find somewhat esoteric: noise...for the fish. I have long felt that providing a comfortable environment should be all encompassing. Water chem..check. Temp...check. Hardscape, hiding places, open spaces...check. Noise.........Noise? Yes, noise. Although I cant prove it scientifically, I have to imagine that living a entire life with that incessant DRONE of an impeller pump has to get annoying for them. Canisters are simply the most practical way of getting that "in-tank" noise as low as possible. Internal filters are the worst of course, followed very closely by any HOB.