Anemonefish (family Pomacentridae) are also known as "clownfish" because pf their characteristic waddling action. They have intimate contact with sea anemones within whose tentacles they shelter. The fish develops a mucous covering to its skin, which appears to prevent the stinging cells of the sea anemone from firing due to the presence of something within its tentacles. Some clownfish depend on a sea anemone more than others, however. All anemonefish begin life as males and remain so as long as a female is present in the host anemone. If the female is lost, the dominant male changes to a female. This ensures that a female will always be present in the occupied anemone, the anemones being essential to the survival of the fish in the wild. a natural host anemone has been suggested for most species, but keeping them can be challenging and is not required for success with the fish. Clownfish are one of the easiest marine species to breed in the home aquarium. sexing, too, is no problem, because if you buy 2 juveniles, measuring no more than 1/2 in long, then you can be sure of acquiring a true pair.
Clownfishes are small and hardy. They are found in tropical areas of the Pacific and Indian Oceans (Red Sea included) but are absent from the Atlantic Ocean. The one disadvantage of keeping these fishes is that they are not really "happy" unless provided with an anemone. The aquarist is then faced with keeping both animals alive.
The Common clownfish is a true darling of the aquarium world and one of the most widely recognized marine fish in the world. Its brilliant coloration and "comic" mode of swimming endears it to all. Hailing from the Indo-Pacific region, this clownfish reaches length of 3.2 inches. It is quite protective of the anemone in which it lives, and generally only one pair per tank can be maintained. It accepts a wide variety of dried and frozen foods. If you are considering a common clownfish, be sure to select a captive-bred animal. While they will live well alone in the aquarium, experiments in the wild have shown that clownfish without anemone hosts are quickly eaten by larger fish.