Hi there! I know this is a super general question. But I wanted to ask because personally I'm fairly confused. Here, on live aquaria, they have "assorted apistos" for sale. I would have thought different apistos require different tank parameters, tank sizes, etc.? If I were to purchase from here, exactly how many can I order for my 37 gallon tank? The tank is 30 L x 12 W x 22 H.