Ok. It seems like Viejas, Red Terrors, and Parachromis are the consensus. But I have a few questions. Would having more than one Vieja lead to fights between them? I doubt I could pull off a pair of Red Terrors in there. So would two of the same sex work or would one lone RT be best? One more thing, with the potential sizes of these various fish, would about 4-5 be the limit for the big boys?