I tried it ONCE, only 50 % and 50 fresh. It's not worth it. The peat has decomposed too much and clogs up the porosity of the soil I think it screws up the Ph too. I recycle out all the perlite only now. I dump the old soil into a big tub of water and skim of the perlite with a strainer (it floats !) I mix that back in mostly for the top half of the pot, I prefer the feeder roots grow down into fresh Pro Mix.I would like to reuse my my pro mix can I and what do I have to do if anything thanx in advance