you don't need to with PBP cause it is a all-in-one formula. That is why PBP is so good for beginner hydro users and/or soil. Don't listen to anyone telling you that you may need anything besides PBP they are lying it has everything you need in that one bottle, the only supplement I ever used along side PBP was Liquid Karna and that I recommend getting it is worth its weight in gold.
