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Zoanthids

Zoanthids ('zoas') are button-like colonial polyps in wild neon colours that reefers collect like stamps, growing in spreading mats on rock.

🗓️ Last reviewed: July 2026

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Overview

Zoanthids ('zoas') are button-like colonial polyps in wild neon colours that reefers collect like stamps, growing in spreading mats on rock. They are hardy and beautiful - but many carry palytoxin, one of the most poisonous natural substances known, so they demand real respect when handled. (Zoanthus and Palythoa species.)

Origin & Habitat

Shallow tropical reefs worldwide, encrusting rock and rubble in bright, surgy water.

Appearance

Flat discs of tightly packed round polyps ringed with a skirt of short tentacles, in electric greens, oranges, pinks and multicolour 'morphs' with collector names.

Placement & Temperament

Peaceful and slow-spreading; can be placed near other soft corals. Some Palythoa can slowly encroach, so give prized neighbours a little room.

Tank & Water Conditions

Salinity 1.024-1.026, 24-27°C, stable alkalinity 8-11 dKH, calcium 400-450, magnesium 1300-1350.

Lighting & Flow

Low to moderate light (about 75-150 PAR) and moderate flow bring out the brightest colours.

Feeding

Photosynthetic; benefit from occasional tiny meaty foods but do not require target feeding.

Health & Growth

Very hardy. Main threats are 'zoa-eating nudibranchs' and other pests - dip new colonies before adding them.

Pros & Cons

Pros

Spectacular collectible colours
Hardy and forgiving to keep
Slow, well-behaved spreader

Cons

⚠️ Palytoxin risk when handled
Pests (nudibranchs, spiders) hitchhike in
Prices for rare morphs get silly

Zoanthids - frequently asked questions

Are zoanthids dangerous?

They can be. Many zoas and palys contain palytoxin, a severe poison. Always wear gloves and eye protection when fragging or scrubbing them, never boil or heat-treat rock that has them, keep the room ventilated, and keep hands away from your face. If exposed - especially to eyes or a cut - seek medical help. Keep them out of reach of children and pets.

Why are my zoas melting or disappearing?

Often zoa-eating nudibranchs or 'zoa pox'. Inspect closely and dip new frags in a coral dip before they ever touch the tank.

🧠 Test yourself: guess the exotic

Three clues from our quiz bank, each about another of our exotic. Can you name them?

Clue 1.From a single island nation, this glossy brown roach gives live birth and males sport bumpy 'horns.'

Clue 2.One of the world's largest land mollusks, this shelled creature can grow as long as an adult's hand and is a serious invasive pest.

Clue 3.A slow-moving herbivore whose elongated body resembles a branch; it may sway gently to imitate a twig in the breeze.

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