I have been in the hobby for just over a year now, with a simple 20 gallon Von Rio Tetra tank, and just picked up a free 40-gallon breeder from a friend. I have been wanting a 55/75 gallon for a long time but happened to come upon this. It's a bummer knowing that half the fish I wanted to keep I can't keep in the 40 gallon, but I'm in the market for some "smaller" cichlids, as I want the tank to only be cichlids (possibly rainbow's or algae eaters). Some cichlids that I saw and liked were the T-bar cichlid, Rainbow cichlid, Electric Blue Acara, Nanocara Anamola, Keyhole Cichlid, Firemouth cichlid, Pelvichachromis (Kribs and Subocelotus), Flag Acara, flag cichlid, Apistogramma Panduro, Geophagus Altifrons, etc. One question I have: Are there any Geophagus species that can be suitable for a 40 gallon? Also, should I be getting pairs of these fish for a community, or just single specimens? If so, male or female? I am also a little bit lost on the stocking amount. Can someone tell me approximately how many of these cichlids I can keep without having territory/heavy bioload? I will, at the same time I first cycle my 40 gallon, will have a "quarantine/separation tank" that's a 20 gallon long for new fish/bullys, and for fry (if I get pairs). I am also really interested in different cichlids than the ones I listed! Thanks.