I've been watching two Ptychochromis oligacanthus in my 32 gallon tank for a few days. They're very small still, the biggest barely being 2 inches long. One of them has gone very dark, almost black. Charcoal grey almost. The other has developed an orange stripe across the top of its dorsal fin, this just this morning. I found them both at the bottom of the tank, as though looking for something, sort of milling around, going in and out of the nearby flower pots. It looks like one is trying to clean one of the flower pots off. The largest one will sort of charge sideways and sidle up to the other one, then back off again. Very cool! Yesterday they were lip locking and 'facing off' a lot, and chasing everything else away from them. This is my first realy experience with cichlids of the same species in one tank, so I'm excited regardless of what it's about lol.