I had a gibbeseps pleco in with my mbuna and i had to remove him. reason being, he wasn't getting any food. i don't really have any major algae for him to feed on, and even if i did the mbuna would graze it away. and anytime i tried to drop sinking food (shrimp pellets, algae wafer, or whatever) the cichlids would totally dominate it and would hardly let the pleco get any at all.
maybe my pleco was just a wimp, but i had to take him out, as he wasn't able to get any nutrition and looked like hell. his fins too were pretty badly torn up, though i was never sure if it was because of lack of nutrition or nippage or a combination of the two. right now he's in a 10g getting nursed back to health, then i'm bringing him back to my LFS so he can get a bigger/better home.
not to mention the pH requirment difference that i failed to notice. plecos liking it a little bit acidic to neutral, and the africans being high.
