I would steer clear of a Jag pair, at least if your gonna make this tank your permanent home. Males have the capability of reaching 16+" and an 18" wide tank leaves not too too much room to be comfortable... It will work, but I would rather a larger fish have that little extra moving room if you catch my drift. Texas cichlids would be cool (cyano cuz they would fill the tank a bit more than Carpinte), but Escondidos are a very attractive fish and would fit nicely in that tank.