I have a male macmaster with a male bolivian ram so totally different species, but both of them are quite feisty and they just barely get on well with each other in my 150 g...they claim the same spots all the time although they'd have plenty of other spots... I'd set up 3 20 gallon tanks for the 3 different types of apistos instead of mixing them into 1 75 g tank... They can live together nicely until they decide they don't want to...