Since clownloaches, reaching over a foot in length, would hardly be suitable for this tank I'd look at synodontis instead. Syno. Petricola and Multipunctatus work particularly well with Africans, but there are many species that will do the job. For pleco's, bristlenose is the best option.
But don't get it just for clean up, get them because you like them. I can assure you that africans will leave nothing uneaten - your loaches or catfish would need to be fed because they won't find much to live off of otherwise. The plecos will help with algae, but algae in an mbuna aquarium promotes the natural grazing behavior that 'clean' tanks miss out on.