The art of camouflage

This is Otto, a South American catfish, properly known as Otocinclus. He and his two colleagues play an important role in our tropical fish tank, hoovering up unwanted algae and generally keeping the place clean. He is beautifully camouflaged, dark and blotchy on top so that it is hard for predators to spot him when he is feeding on the bottom, and silver underneath so that he blends in with the bright surface of the water when seen from below.