Clownfish (Amphiprion ocellaris): Facts, Anemones and Habitat

How to recognize an ocellaris clownfish

The ocellaris clownfish has a short, oval body that is flattened from side to side, a rounded head and a rounded tail. Most are bright orange to reddish brown with three white bars: one just behind the eye, one across the middle of the body that bulges forward toward the head, and one around the base of the tail. Every bar and every fin is edged with a thin black line.

Not every wild ocellaris is orange. Off the Northern Territory of Australia there is a natural black form, with the same three white bars on a black body. Aquarium breeders have also produced many color variants, with missing, merged or extra-wide bars.

The genus name Amphiprion comes from Greek words meaning “saw on both sides”, a reference to the tiny saw-like edges on the gill covers. Clownfish belong to the damselfish family, Pomacentridae, and are also known as anemonefish.

Ocellaris clownfish vs orange clownfish

The orange clownfish (Amphiprion percula), also called the percula clownfish, is the ocellaris clownfish’s closest relative and looks almost the same. The surest difference is in the dorsal fin: the ocellaris usually has 11 spines (rarely 10), while the orange clownfish has 10 (rarely 9). The ocellaris also has a taller spiny dorsal fin, and its black edging is thin, whereas the orange clownfish often has thick black borders around its white bars.

The two species mostly live in different places. The ocellaris lives from the Andaman Sea to the Philippines and northwestern Australia, while the orange clownfish lives farther east, in northern Queensland, including the Great Barrier Reef, and in Melanesia, such as New Guinea and the Solomon Islands.

How big do ocellaris clownfish get?

Ocellaris clownfish are small. Adults average about 8 cm (3.1 in) in length and reach a maximum of about 11 cm (4.3 in). Their weight is rarely recorded, but a fish of this size and shape weighs only roughly 7–20 g (0.25–0.7 oz).

Size in a clownfish group is not random. The breeding female is always the largest fish, the breeding male is second, and each younger fish is smaller than the one ranked above it. Lower-ranking fish actually hold back their own growth so they do not provoke a fight with the fish above them.

Habitat and range

The ocellaris clownfish lives in the tropical eastern Indian Ocean and western Pacific. Its range runs from the Andaman and Nicobar Islands, Thailand and Malaysia to Singapore, Indonesia and the Philippines, south to northwestern Australia and north to Taiwan and the Ryukyu Islands of southern Japan. It does not live in the Atlantic Ocean or the Caribbean Sea.

Within this range it lives on coral reefs and in calm, sheltered lagoons, from about 1 to 15 m (3–50 ft) deep. Above all, it needs a host anemone. In the wild, the ocellaris clownfish uses just three host species: the magnificent sea anemone, the giant carpet anemone (Stichodactyla gigantea) and Mertens’ carpet anemone (Stichodactyla mertensii). These anemones grow in shallow, sunlit water because they rely on tiny algae living in their tissues, so the fish stays shallow too. The full picture of where the different clownfish species live is in Where do clownfish live?

Life inside a sea anemone

An ocellaris clownfish spends almost its whole adult life within a meter or two of its anemone. The anemone’s tentacles are armed with stinging cells that can stun and kill small fish, but a clownfish swims among them unharmed. Its protection comes from a special mucus coating on its skin, and a newly arrived clownfish usually goes through a short acclimation period, gently touching the tentacles with its fins and belly before it settles in. How that protection works, and what scientists still argue about, is explained in Why don’t clownfish get stung by anemones?

The partnership is a classic example of mutualism, in which both partners gain:

• The clownfish gets a safe home for itself and its eggs, protected by tentacles that most predators avoid. At night it rests deep among the tentacles.
• The anemone gets a guard. Clownfish chase off fish that bite anemone tentacles, such as some butterflyfish, and remove parasites. Their fanning stirs the water around the anemone, and their waste provides nutrients; in one 2005 study, anemones with clownfish grew and regenerated faster than those without.

What do ocellaris clownfish eat?

The ocellaris clownfish is an omnivore. It feeds mainly on tiny animals drifting in the plankton, such as copepods and the larvae of tunicates, and it also eats algae. Studies of its diet suggest it takes plant and animal food in roughly equal amounts. It also picks up scraps of food the anemone has not finished and eats small parasites from its host.

Feeding follows the pecking order. The big breeding pair swims farther from the anemone to catch food, while the smallest fish stay close to the tentacles, where they are safer but find less to eat. Clownfish have been seen carrying pieces of food that are too large to swallow back to their anemone.

Social life: groups ruled by size

Each anemone holds one clownfish group: a breeding female, her breeding male and usually a few smaller non-breeders. The members are generally unrelated; they are fish that arrived as young and found a place in the queue. The female controls the group through aggression and keeps the males from changing sex, and the breeding male in turn keeps the non-breeders from maturing.

Clownfish keep this order with chases, displays and sounds. They make clicks, pops and chirps, probably produced by snapping the jaws and amplified by the swim bladder. A subordinate fish signals submission by shaking its head.

Ocellaris clownfish are protandrous hermaphrodites, meaning that breeding fish are male first and can become female later. If the female dies or disappears, the breeding male changes sex and becomes the new female, and the largest non-breeder becomes the new breeding male. The details of this switch are covered in Can clownfish change sex?

Reproduction and life cycle

The breeding pair is monogamous and stays together on the same anemone. In tropical waters they can spawn almost year round, with spawning concentrated around the full moon. Before spawning, the male clears a patch of bare rock close enough to the anemone for its tentacles to protect the nest, then courts the female by chasing her, nipping her and spreading his fins.

The female lays about 100–1,000 orange eggs over one to two hours, attaching each one to the rock with fine threads, and the male fertilizes them. He then does most of the parental care, fanning the eggs to keep oxygen flowing and eating any eggs that are infertile or attacked by fungus. The eggs hatch after about six to eight days, usually at night; cooler water slows their development.

The newly hatched larvae drift up into the open water and spend about 8–12 days in the plankton. They then sink to the reef as tiny juveniles and search for a host. Experiments show that ocellaris clownfish recognize their host anemone by smell, a cue they seem to learn as embryos in the egg. A newcomer joins a group at the bottom of the hierarchy and is often chased out if the anemone is already full.

Lifespan, predators and threats

The lifespan of wild ocellaris clownfish has not been studied closely, but it is estimated at about 6–10 years. In captivity, one has been recorded living to 12 years, and some are reported to have lived beyond 20. For a small fish, clownfish are long-lived: field studies of the closely related orange clownfish estimate that breeding females can live around 30 years.

Most clownfish die young. Eggs are eaten by wrasses, damselfish and brittle stars, larvae drifting in the plankton are eaten by many predators, and juveniles that fail to find an anemone rarely survive. Adults are fairly safe as long as they stay close to their host.

The main modern threats are:

• Anemone bleaching. Host anemones bleach in marine heatwaves in the same way that corals do, and bleached anemones may shrink or die, leaving clownfish homeless. Learn more in What is coral bleaching?
• Ocean acidification, which can dull the sense of smell and hearing that larvae use to find reefs and anemones.
• Collection for the aquarium trade, which has reduced local numbers of ocellaris clownfish and their anemones in heavily fished areas.
• Coastal development, which adds sediment and pollution to shallow reefs.

Conservation status

The IUCN Red List assesses the ocellaris clownfish as Least Concern (assessment dated 2021). The species is widespread and still common across much of its range.

Local declines are well documented, though. A 2014 study around the Spermonde Archipelago in Indonesia linked lower numbers of ocellaris clownfish and their host anemones to collecting for the aquarium trade. Clownfish are more abundant in marine protected areas where collecting is forbidden. The ocellaris clownfish is also one of the easiest marine fish to breed in captivity, and captive-bred fish now supply much of the trade.

Clownfish and Finding Nemo

The 2003 Disney and Pixar film Finding Nemo made the ocellaris clownfish one of the best-known fish in the world. It was already a popular aquarium fish: between 1997 and 2002 it was among the most traded marine fish worldwide, and in 2011 it made up almost half of all clownfish imported into the United States. A 2017 analysis found no clear evidence of an immediate jump in wild-caught clownfish sales after the film, although its popularity has stayed high.

The film took some liberties with the biology. Real ocellaris clownfish do not naturally live on the Great Barrier Reef, where the story is set; the orange clownfish lives there instead. And when Nemo’s mother died, the real Marlin would have changed sex to become the female of the pair.