Im not positive, but I do know they grow really fast! You are going to need a bigger tank for them or else they will start taking out each other. I have my (6) baby RBs in a 40 gallon tank and will be moving them into a 150 gallon shortly. My advise is to get them into a bigger tank before you are sorry.
Space does play an important role in growth of your Ps, as well as propper feeding. Trust us about getting a bigger tank for your fish even at the size they're at for the momment. Hope your 5 P's are Pygos.