I've often been confused with the myth of canister filters for that reason. They're only nitrate factories if you toss in bio balls, filter media, etc. I don't see a difference in that versus having a closed off HOB for LR and some macro, other than the fact that lighting a canister would be much more difficult.
However, they would in turn act like a fluidized bed filter, in that they would cause great amount of water to flow through a filter that won't turn your tank into a melting pot for baddies.
PERSONALLY, I wonder why I didn't think of using 2 canister filters for my overflow and return - Sure would have saved a hell of a lot of headache. Yes it's two more things that could possibly fail, but the setup and implementation is pretty logical and seems that it SHOULD work... maybe?
