Best rocks for algae growth.

Hi everyone, I am setting up a new tank around my little t. duboisi and was wandering which rocks to choose to grow algae on, the red lava rocks or flat slate-like rocks? Also I here that you shouldn't mix tropheus with mbuna, but I can't find a definitive answer as to why. I understand that the water maybe slightly different chemically and diet may pose a problem but there is some overlap. Is it just a matter of aesthetics or is there a "real" reason not to mix them? What I'm looking for is the "poorman's" reef type aquarium, don't laugh.

Thanks guys for the info, I was thinking the red lava rocks. @duanes btw I was only going to put some red zebras, acei, yellow labs, brichardi and socolofi in with them. Would these be ok?

Thanks guys, I've heard about them being best in a group of other tropheus but my mom picked him/her up during the Petco 50% off sale, so after my employee discount it came up to being about $5 rather than $35. That was the only one that they had and now if they get anymore they will be $35, which is ok but I wanted the colors of mbuna. That's why I was asking about the more "peaceful" types.

Then again would peacocks work better than mbuna? My girlfriend has credit at the store that she works at, so we can get about 5.