That's the 'common pleco' aka "Bandaraya". Most likely a Sailfin Pleco - pretty common in M'sia.
Should get along fine with your Mbunas - I've had mine for years.
UNLESS you have not been feeding your fish enough, they MAY turn on the Pleco. The Pleco normally is able to defend itself, but in my experience they have become food before (if you can talk fish, you can probably ask my Malawi cichlids why they attacked/ate my common pleco in 2004).
