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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.Kept as a low-maintenance pet abroad, this slow nocturnal animal needs calcium to build its huge spiral shell.

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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