Clownfish are usually bright orange; occasionally they will be brownish. They have three large white stripes on the body with black edges. They grow to about 8 cm (3 inches) long. They have a single nostril on either side of their snouts.

Family – The clownfish belongs to the subfamily Amphiprioninae within the Family Pomacentridae. Within the Amphiprioninae there are 29 known species, 28 of each belong to the genus Amphiprion, including the clownfish.

One of the most remarkable qualities of the clownfish is where it chooses to spend its time: amongst the waving tentacles of anemones whose nematoccysts (stinging cells) are lethal to most other fish. The clownfish is able to swim comfortably in and out of the anemone due to the mucus it secretes, which prevents the nematocysts from discharging. The clownfish generally associates with the anemone species Heteractis magnifica, Stichodactyla gigantean and S. mertensii This relationship is symbiotic as the two species are able to live together. This interaction is often cited as an example of mutualism, where the two species both gain from their association. While there is no doubt that the clownfish needs the anemone for protection and reproduction, some scientists dispute whether the anemone needs the clownfish at all. It has been suggested that the clownfish does help the anemone by eating its parasites and fanning it to increase the circulation of water over its tentacles.

Globally, the clownfish is found from the Red Sea across to the Central Pacific, and is concentrated around the Indo-Pacific area; it lives in warm, shallow tropical seas from a depth of one to 10 metres.

The spawning season for clownfish lasts all year, with one to two weeks between consecutive broods being laid. Eggs, which are elliptical and measure about 2.2mm long and 0.9mm in diameter, are attached to a solid base, usually near the foot of the anemone, by fine threads at the ventral pole of the egg. They are bright orange when newly laid, but fade to grey or brown until immediately prior to hatching when a silver sheen becomes apparent due to the developing eyes. Parents guard the eggs until they hatch; this takes seven days.

Clownfish usually hatch about half-an-hour to two hours after sunset; this is thought to be an anti-predator strategy. When the larvae break out of the egg, they rise to the surface and begin the planktonic stage of their lives.

When they descend back down into the water, the clownfish must find a suitable anemone in which to live. It was thought for a time that anemones were occupied by a single pair, consisting of a male and a female, but it has since been found that this is not strictly true. An anemone usually contains a dominant female, a smaller male who is subordinate to the female, and several small neuter individuals that rank below the male. If the female dies, the male changes sex and becomes the dominant female. The neuter individual that is immediately below the male in rank will change into the male. Juveniles who have just descended from the surface will become neuter individuals, unless a higher place is available. Juveniles do not mature sexually until they are large enough to develop mature gonads and replace one of the dominant pair. Multi-male, multi-female groups are rare, and are generally found where there is an unusually high density of clownfish, due to either the large size of the host anemone or an extreme abundance of the fish.

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