Well, I have two Alligator Gar in my tank currently and I've had them for a little under a year but they are actually very easy to keep and are much more entertaining than a documentary would suggest. All that I have really done was made sure the PH stayed good, added flora and a drift log. I have housed with them 1x Shovelnose Catfish, 1x Largemouth Bass, 2x Channel Catfish, 2x Black Crappie, 4x Sunfish(Bream), 2x Plecostomas, and about 6x Crayfish. All of my fish get along very well and are fed shrimp pellets, smaller crayfish caught from my creek, minnows(both wild and storebought), algae tablets, small bream caught during minnow harvest, and occasional worms/goldfish. I have white/brown pebbles as a substrate along with a few rocks that have been found from our creek. The tank has a full bubble wall in the back, a heater, and an undergravel filtering system. My tank is 48" left to right, 32" back to front, 50" left front to right front(bowfront), 23" tall(I'd tell you how many that is in gallons but I can't for the life of me remember how to convert cubic inches to gallons. I really hope this helps. Good luck finding any better advice!