Is there a 3" deep mechanical filter??


I am running a 72bow, with a Oceanic 75 plus wet/dry system, UV, and AquaC protein skimmer, and the water is clear but it seems like I can always see little particles in the water. I have a built in overflow with pre filter and it doesn't seem to suck the water in enough to rid of all the particles. I am also running two powerheads for water current and to keep the stuff off the bottom. I wanted to add a mechanical filter off the back of the tank, but only have 3" of room. Does anyone know of a filter only this thin.