Istlanus is the lone endemic cichlid in its riverine habitat along the Pacific coast of Mexico.
This loner situation usually means it will be intolerant of other cichlids, so is best kept in a large species only set-up (a non-cichlid community).
Much like M beanii (which lives in rivers just to its north, or other loners like haitiensus, when put in community situations it attempts to kill all other cichlid tank mates, and if it can't destry them, the stress causes it to bloat.