+1 on the Aquaclears; I have them on my 10g and my 29g tanks. I would get a canister for larger tanks, but the HOBs work fine on smaller low tech tanks. Aquaclears do have space for lots of media options, and they have adjustable flow rates. They're reliable, and tend to be pretty quiet.If you do go HOB, Aquaclears are the way to go. They have a big media area and you can put anything you want into them without using expensive premade cartridges that most HOB filters use.