Anemonefish

Clownfish vary in size; the maroon clownfish can reach 160 mm (6.3 in) long while the orange clownfish reaches only 80 mm (3.1 in). Females are larger than males and the smallest individuals in a group are only 6–15 mm (0.24–0.59 in). Clownfish vary from oval-shaped to streamlined, and have rounded heads that lack scales between the snout and eyes. Teeth are present on both the oral and pharyngeal (throat) jaws but absent on the palate, and may be conical or chisel-shaped. Clownfish have saw-shaped edges along the operculum (gill covering) and under the eyes, which is the source of their genus name. The dorsal fin has 10 spines followed by 14–20 soft rays. It varies in shape; the ocellaris clownfish has a large recess between the spines and soft rays, while in the red saddleback anemonefish they are mostly continuous.

Clownfish inhabit warm and tropical waters spanning the Indian Ocean and the western Pacific; from the Red Sea to French Polynesia, and from Japan down to Australia. Some species are more widespread than others, and some live only around islands or archipelagos. Areas closer to the edges of their distribution have fewer species; both the Red Sea and French Polynesia have only one species each. By contrast, as many as 12 species can be found in an area in other regions such as Southeast Asian and northern Australian waters.

Clownfish are omnivorous, and mostly feed on planktonic food such as algae, copepods and larval tunicates. Algae makes up much of the diet of the pink skunk clownfish. Clownfish also feed on the waste discharged by the anemone. Feeding takes up most of a clownfish's daily activity. Where predators are less common, clownfish may forage in an area as large as 20 m2 (220 sq ft) around their anemone. Otherwise they are restricted to feeding in the water column above their host. The dominant pair in a clownfish group feed further from the anemone than the smaller subordinates.

Clownfish breed year-round in tropical waters while in more temperate waters, like those around Japan, breeding occurs mostly in spring and summer. Only the dominant female and male reproduce, which mostly occurs during a full moon. In the days leading up to spawning, the pair perform courtship rituals that involve the male chasing and nibbling the female as well as erecting his dorsal, pelvic and anal fins while staying motionless in front or alongside her. Both the female and male then prepare a nest by cleaning up a nearby rock. Here the female deposits eggs for the male to fertilise. Clownfishes lay up to a thousand eggs, which are conical in shape, 3–4 mm (0.12–0.16 in) long and stick to the rocky substrate by bundles of short fibres. The male tends to the fertilised eggs, cleaning and guarding them as well as fanning them with his pectoral fins.

As of 2025, 25 of the 29 clownfish species along with the hybrid white bonnet anemonefish are assessed by the IUCN Red List; most are classified as Least-concern except for Mccullochi's anemonefish, which is classified as Vulnerable. Additionally, the wide-band anemonefish is listed as Data Deficient. Threats to clownfish populations in the wild include ocean warming and acidification, exploitation for the aquarium trade and human development along the coast; the first two are linked to global warming.