Black anemonefish (Amphiprion melanopus) in their host anemone. The female (right) is far larger than the male (left). This fish, also known as the fire clownfish, is found on the coral reefs of the tropical Pacific Ocean. It lives in the stinging tentacles of a sea anemone, to which it is immune. This affords it protection against predators, which would be stung by the anemone. The fish picks parasites from its host anemone, thus forming a symbiotic (mutually beneficial) relationship with it. The black anemonefish can reach a length of around 12 centimetres. It is sometimes sold in the aquarium trade. Photographed in Sulawesi, Indonesia.