Best set up for Mbuna

[Tomo]

Looking to set up a mbuna tank, have got coral sand as a substrate but was wondering what is the best rock set up for them?. Got given some Lava rock which will look great against my 3D background but it looks very porus with lots of very small holes will algae still be able to grow on lava rock? because I know mbuna like to graze on algae, or is it best to get plain rock with a smoother finish for the algae to grow, just want to get the right more natural set up for them. Would appreciate any advice thanks