Be very careful with the Tropheus if you're going to do that... since I've not had personal experience with any types of Tropheus... But the one thing that Herbivorous fish really really like meaty foods... Like my Eretmodus, I've been really careful what I feed him... and Yes that is one thing I've heard about the crab...They can be very aggressive... But good luck with the Tank... Lots of Rock Piles for all your Rock Dwellers... lots of open space if you get Cyprichromis... Get some pictures up?