FWIW, with regards to rocks it's either one extreme or another IMO. I've seen plenty of rockless tanks with large tropheus breeding to know it works. If you want rocks, I'd say the more the better. I know they aren't tropheus, but it's a similar issue with Ps. demasoni and filling the tank full of rock is what it took me for success.
In my bemba tank I have a single large rock to split the tank 1/3 and 2/3rds - dominant male takes over the 1/3 portion and keeps the rest on the other side for the most part. If not for the rock creating some sense of a divided territory I suspect he'd probably push the rest a bit further.
