I have driftwood in my crushed coral substrate 40g and it's fine. Cant put it in my 110g with black sand, the ph nose dives. In my experience with Mbuna, Peacocks and Haps. My Mbuna never breed, because I didn't have enough females nor find any to buy. Almost all of them look the same when juveniles. Haps and Peacocks, in my opinion are allot easier to sex. My experience with Mbuna, if you want to breed, stick to one species that you can buy 5 or 6 in hopes of getting some females and males. Yellow lab males usually have more black on the fins than females. I've never been able to house even in my 110g yellow labs and Red Zebras together, 24/7 they chase eachother and when they get going I've had to literally save one cause they crashed into a rock and it got stuck underneath, so watch them and be careful because when they are ready to breed,you will know because you'll wake up to most likely chaos. (Which is normal) like others have said, it's not so much getting them to breed, it's what to do with all the fry. Because they will breed, my Haps and Peacocks don't care if I'm cleaning the tank, draining it ect.. they don't care nor stop. Lol.