In AC70's, I run 2 foam blocks and a bag of some sort of bio (either bio-max or matrix). In my AC110's I have one set up with foam and bio and one with 2 blocks of foam.
I find that this works well, as I haven't had any water quality problems for ages. I also run multiple filters on my larger tanks and alternate cleaning. This also helps when setting up new tanks, as all I do is take the media basket from a running filter, pop it in a new AC70, and instant cycled tank.