I agree that there's not a lot of difference between canister filters and hang-on filters in terms of biological and particulate filtration. I just like the out of the way aspect of canister filters. I don't get what's so great about the Bio-wheel type. It appears to have both slide in type filter pads as well as the 'wheel', which adds extra biological surface area, but why this is better than a hang-on filter with bigger pads I don't know. I would imagine the 'wheels' cost more than the pads to replace so that is one thing I don't think I'd like about them. I have Tetra hang-on filters as well as canister filters and the hang-on ones have both slide in pads that you can fill with charcoal and a pretty cool system that periodically dumps in the water after it goes through an extra sponge of biologically promoting material, and it also has a replaceable built-in heater that is shielded against overheating when there is no water to keep it cool which is very nice. I've blown many heaters when I've forgotten to turn them off during water changes so that sold me on Tetra hang-on filters. So, I really think the main thing is to look at how much surface area your filter provides for beneficial bacteria to grow and thus clean the waste the fish and other organisms produce from the water. The black sponge material and I guess I've seen white sponges of different pore size look to me to be a very good substance to grow bacteria on, I would think better than cotton type pad or bio-wheel material, and also the other things like ceramic stars, tubes, etc that go in canister types which can't be put into hang-on filters. Many canister filters are awkward or messy to clean I admit, but they're still my choice for best filtration and looks, and I'm not always buying new filter components when I go to the aquarium store. PS I love you quote 6atreyu9 "Bombing for peace is like f**king for virginity".