Nandopsis grammodes. "Smaller" guapote, adult males can reach 10-11+" SL. Very aggressive piscivore. Found in rivers in nature, so any current in the tank won't bother them at all. Feed only low-fat foods, they bloat easy (most Nandopsine fish do). Keep water extra clean as they can be sensitive to "dirty" water. Did I mention they are aggressive? Well, they are. I wouldn't keep one with a managuense, sooner or later you'll have a problem.
edit: where did you see/hear them called "sieve" cichlids? That's a new one to me.