I also would not suggest a pleco in any African cichlid tank, but especially not a rubber lip. My first question is why would one be needed? African cichlids are heavy vegetarians and will pick at and eat most types of algae that would grow in their tank. Beyond that, algae removal should be done manually with a blade tool or razor blade.
If the tank water is in good standing, most algae species wouldn't become an issue to start with. If your wish to add the pleco is to maintain the tank, the first thing I would do is check water params for ammonia, nitrite, nitrate, and pH, and phosphate, and the second thing I would check would be the lighting, both amount of light (wattage) and length of light cycle in a 24 hr period, and also age of bulbs. Aquarium light bulbs should be changed out at least 1 - 2 times/yr, depending on the type of lighting it is.
Hope this helps.