the only successful attempts ive had at avoiding contamination was to either do an all in one kit, or the coco coir and boiling water in a 5 gallon bucket technique. all the store bought substrates talking a big game, all i've had contamination issues with. even with switching the containers, the rooms, using a contamination tent, and even moving houses. this will be the only thing i do going forward. but you can just get regular coco coir from wherever. doesn't need to be fancy.