www.animalworldnetwork.com/flfx5hipecaf.html
there's one of the favorite canisters around.
It nothing more than a big external filter, which has the possibility of "Out-of-tank-maintenance."
and it can be DIY, but imo it's not worth the effort.
Building a sump is easier!
I just read your other thread and you said you're looking for a new tank, for the other one you were gonna buy was cracked by it's owner, before you got it.
Best shot is to get a new tank that's running with a sump allready.
I bought my tank, including the sump, and never regretted it.