The Real Story of Clownfish

Thanks to a certain animated movie, clownfish are one of the world's most famous fish. But the real life of a clownfish (Amphiprioninae) is far stranger — and more interesting — than the movie lets on.

How Do Clownfish Live Inside Anemones Without Getting Stung?

Sea anemones are venomous — their tentacles sting and paralyze prey. But clownfish have a thick mucus coating that prevents the anemone's stinging cells from firing. They also gradually acclimate to the anemone by gently touching it, building up a thicker mucus layer. In return for shelter, clownfish keep the anemone clean of parasites and their movements improve water circulation.

Can Clownfish Really Change Sex?

Yes — and here's the part the movie got wrong. All clownfish are born male. In each group, the largest individual becomes the sole female. If she dies, the dominant male changes sex to become female and takes her place. In Finding Nemo, when Nemo's mother died, Marlin should have become female.

How Big Are Clownfish?

Clownfish are small — most species are 3–5 inches long. There are 30 species of clownfish, ranging from the iconic orange-and-white to yellow, red, black, and multicolored varieties. They are all found in the warm waters of the Indian and Pacific Oceans.

What Do Clownfish Eat?

Clownfish are omnivores — they eat algae, plankton, and small invertebrates. They also eat undigested food, dead anemone tentacles, and parasites from the anemone, making the relationship a true mutualistic symbiosis.

Amazing Clownfish Facts

• Clownfish never stray far from their anemone — usually within 3–4 feet.
• They are territorial and will aggressively attack fish far larger than themselves that come near their anemone.
• The female lays eggs on a flat rock near the anemone; the male guards and fans the eggs until they hatch.
• After Finding Nemo was released, demand for clownfish as pets spiked dramatically — causing wild populations to decline in some areas.