I have a 55g that is newly setup. I don't have any fish in it, the sand has yet to settle. I plan on getting Apistogramma Cacatuoides as my first choice, but if I can't find them then I'll get Kribensis. How many of each gender for the 55g? I know that the Apistos are harem breeders, and the Kribs pair bond, but exactly how many can the tank hold without them attacking each other? I plan on the tank being a biotope, or only using fish in it that would naturally share the same waters as in the wild.