Hey Alex, in hind sight I probably didn't need a radial flow filter for this system I guess I just got caught up in building stuff but I figured that since that is where most of the solids will end up it could be a good home for a couple of crayfish, and your probably right about the snails they could just go wherever they wanted. I am planning on putting red worms in as soon as the plants get a little growth on them. While we are at it do you Alex or anybody else have any thoughts or info on natural/organic inputs to help add nutrients to the system, I've read of some people using egg shells and lime juice to control PH and using dried banana peels for potassium, what about potash and other soil amendments would they work and be safe for the fish?