They get to roughly 15cms.. Ph of around 8.2, like the tank a little on the warmer side, around 27-28 degrees... however I have mine around 26-27, very happy.
They come from Lake Malawi.. you can house them quite happily with other Mbuna, Peacocks etc...
Definately don't keep Africans with Americans, I know some do, but I don't go advocating that, they need different water parameters etc..
And also, just a quick note, it does pay to get a bit of background of info on a fish if you are getting it from another fish keeper or they should have really given you the info to be honest, or even if you find something in the store, read about it first