All the Fluval is a modified Aquaclear. I have two C4's and love them. They have taken the mechnical and turned it vertical the pad has both a regular aquaclear foam plus a fine pad added on which the aquaclear lacks. The media basket in front has plenty of room for anything else you want, carbon, additional bio, etc. Plus you have a neat small trickle filter. The only issue is the C4 is compairable with the AC70 and they make no Fluval C that's the size of the AC110 or old 500 I wish they would it would be one awsome filter. But the C is a nice filter I'd take it over my AC70.