No he's right substrate does not effect potency.. What you probabily experenced was different genetics or better growing conditions.. For mushrooms to be at there peak potency potential they must be cultivated right.. Bulk spawn only adds more yeild but doesn't effect potency.. If that were the case nobody would even bother with any other substrate..No way man. Poo/compost shrooms (on average) are much more potent than brf cake shrooms. I've done both myself, and substrate means a lot.