The big question is what type of lions do you want? If you want two dwarfs either the Fuzzy Dwarf, Dwarf Zebra, Fu Manchu, then you can do it in a 46 gallon with lots of cover for them to hide and protein skimmer. The big problem with devoting a tank just to lions (unless you do the Volitans which is more of a open water lion as adults) is they are very secretive and hardly move. You might want to think about another small fish like a pygmy angel or something to the like. If you want to go with two Volitans, Russels, you will want to go with a 125 minimum. Radiatas and Antent.... are 75 minimum. Hope this helps. Also be prepared to feed them live ghost shrimp till they get used to frozen. NO FEEDER GOLDFISH!