+1 scrubbies have a ton of surface area, are cheap, and easy to clean. Usable in just about any filter. Found this chart on another MFK thread. As you can see they have one of the highest surface areas per cubic footScrubbies serve as great surface for biomedia, both in sumps and canisters. I've used them both ways with great results. For canisters, I've had them in both Rena Filstars and FX5s.