I've seen some impressive pictures of gorgeous rock displays in African cichlid aquariums. What kind of rock is it that they use? I understand the cichlids need hard PH and the rocks also help with that in addition to offering hiding places?

Do you have a picture of one of these tanks you could show us? I'm not sure which you mean.

I'm trying to think of some hard PH rocks. I know texas holey rock is popular, and slate, and lava rock.