If you are looking for the best HOB. By far the FLUVAL C2, C3, C4. I have the C4 on my 40B. 5 stage filter wet dry. The sponge you just rinse/ squeeze in used tank water. It even has an indicator that pops up to say "hey stop being lazy and rinse the sponge." The basket for the carbon is very big. You can put Marine Pure spheres or block in there or use a whole bottle of purigen in a fine particle holding bag as an upgrade and more beneficial. The little piece of cloth on top of the wet dry I leave in and rinse with tap water every 2 days. Simple. Some people complain like it is changing a dirty diaper. Really not a big deal at all. Has a 267gph turnover I believe. Also it is quiet and no vibrations!