filters are simply easier to clean than canisters, and generally move more water for the $$. An aquaclear 50 on a 29 is fine for small fish like tetras and Cory cats. That model pumps around 200 GPH
, which would turn over the actual water volume in a 29 gallon tank 8x/hour.
If you do prefer a canister (not enough clearance behind the tank for an hob
or simply want it out-of-sight inside the stand) I'd recommend an eheim 2215 for a 29. The eheim classic series are simpler and less expensive than the ecco or pro series, and will last for many, many years w/out replacing parts.