Jamie must not have a copy of my DIY CD
My current DIY filter design, is a 4x4 settling chamber made with wood frame and rubber lined. Inside the chamber is a 55 gallon barrel. The barrel is full of slits. Inside the barrel is a center tube, also full of slits. This is where the pump draws its water. The barrel is full of Bickal Bio-rope. Settling chamber takes out the big gunk, bio-rope filters out the fines, and does some bio and the pump pumps out to more bio, trickle tower, or whatever you please.
Cheap, easy, effective.