Those are very cool. I have a pair of xenotilapia flavipinnis - not as colorful, but very interesting. They are sand-sifters as you can see in the video. They scoop up mouthfuls of sand and sift out small organisms like micro-crustaceans, etc. Look them up in the profiles section. Mine have adapted well to high quality flake, and they keep the bottom of the tank clean, sifting out any bits that were missed by the others.