tropheus moori would be good choices for a 30
i'd disagree with that one. Tropheus are quite difficult:
1. they cannot tolerate poor water quality and neither can they adapt quickly to significant changes in their tanks water chemistry. this means that large water changes cause problems. frequent, small changes in the neighborhood of 10 percent are a must. this makes nitrogen waste management difficult since a group of Tropheus feeds almost constantly and contribute a high waste load to any tank.
2. the Tropheus intestinal tract is designed for slow, constant bacterial processing of the large quantities of algae they consume. therefor, unless you have a heavy load of algae in your tank, they must be fed small amounts of spirulina, often. 6 times daily would be about right.
3.
Tropheus species maintain a strict but evolving heirarchy. they therefor need to be maintained in large groups of twelve to fifteen fish at a minimum. not doing so will allow the dominant fish to pick on lesser Tropheus tank mates if there are fewer fish. the aggression can’t be spread around unless you have enough fish.
4.
12-15 fish dictates a tank sizes of 75 gallons minimum. you simply cannot keep Tropheus successfully in anything smaller. a smaller tank does not allow the chased fish to have room to escape the aggresion of dominant fish and eventually the dominant fish will do serious injury or kill the lesser tank mates.
5. Tropheus cannot tolerate stress. you need to change the water the same day of each week and in the same amount each time. turn your light on and off at the same time each day. feed them the same food sequence each time you feed them. basically do the same thing all the time every time.
6. all Tropheus digest their food in a similar manner, bacteria breaking down the food in a long intestinal tract. when a Tropheus cannot digest food properly it stops eating and attempts to discharge whatever is causing the irritation. "Bloat" is the result and left untreated, it will continue to attack the fish until several if not all the Tropheus in the tank die. it's a difficult disease to treat and more Tropheus are lost to this disease than all others combined.
i could go on, but i think you get the idea.