I use pro-mix. I buy a bale every 2 - 3 years. It's very in-expensive compared to the bags of potting mix, and much better quality. There's a pro-mix product which has an added bacteria or fungus (I forget which) which is supposed to eliminate "damping off" issues. The downside of pro-mix is that it has pearlite in it, which my chickens are attracted to. They go crazy picking the pearlite out of my pots. I assume that it is harmless. But, either way, I go to great lengths to keep them out of it.
