No carbon. I use the fluval ceramic coarse pre-filter rings (came with my filters), then filter floss, then two baskets of porous biomedia. Thus, I have the sponge, the rings, and the filter floss for coarse and fine mechanical filtration, this keeps the two baskets of biomedia ultra clean so I never have to change it.
Can peat bags discolor water? If you have to give up something, get rid of the carbon and add other stuff.