I purchased one of these a while back - stunning looking fish.
He was about 6 inches.
I did my research before hand & it seemed they should be fine in my mixed African tank.
Wow... How wrong was that...
On the first night he wiped out any fish that would fit in his mouth.
I tried to catch him that night but couldn't, I wasnt going to take out all of the rocks at midnight...
Next day he had turned his attentions to the Tropheus & was chasing & trying to bite 3.5 inch tropheus..
All rocks were taken up & he was brought back to the shop immediately.
It seems they work out fine for some people, but my one was a killer. I wouldn't go near them if I were you.