Well, I'll tell you what works for me. I use a simple 7"x 16.5" one micron filter sock over the end pipe. It's used as a pre-filter before the bio- media. It's all the mech. filtration I need. On my 240gal. that has 2 overflows, 2 filter socks are used. The one micron socks really polish the water as well. I get them at McMaster Carr for couple a bucks a piece in quanity.