I got one of them canisters for my 20 long, which has 2 sponge filters on it as well and doesn't need superfiltration.
It is a great little thing. Very quiet, easy to put together, does what it is supposed to do.
I have to say this, too. The first one I got had a tiny broken part. I sent a photo of the part to the company to see if they could replace it. They sent me a whole new filter, no charge, within 2 days. I am very, very impressed by their service-and I like their products, too!