The thing with most Plecs is that they are NOT solely algea eaters. They need other stuff, most algea waffers are formulated to give a variety of plant matter, also you may find that you plec may like your cichlid pellets. The key to keeping plecs is knowing that you need to feed it more than just the little bit of algea growing on the rocks. Some hardcore mbuna keepers prefer to allow algea to grow up on the rocks and just clean it off the glass. This provides natural food for the mbuna. In this situation, you wouldn't want a plecko. Also, all plecs come from south america, so they are not exactly biotypical of a Lake Malawi tank, I say this, but I have a clown plec (it stays small and hides most of the time) in my Lake Tanganyka tank.