Zoanthids
Zoanthus / Palythoa spp.
Colour-packed polyp colonies — the collectible, forgiving coral most reefers start with.
Difficulty: BeginnerSoft coral (beginner)
Zoanthids (“zoas”) and their Palythoa cousins (“palys”) are colour-packed button-polyp colonies — the collectible, forgiving coral most reefers start with. They're hardy, fast-growing and come in endless morphs. One serious thing sets them apart from every other beginner coral: some carry palytoxin, a potent toxin dangerous to YOU — so handle them with care.
Care at a glance
| Colony / form | Encrusting mats of button-like polyps that spread across the rock over time. |
|---|---|
| Lighting | Low–moderate — roughly 75–250 PAR. Acclimate to bright light slowly (too much, too fast can shock them); colour is a rough guide to their light preference. |
| Water flow | Low-medium to medium — enough to keep detritus off the polyps, but not so strong they can't open. |
| Placement | Low-to-mid rockwork to start; you can move them higher as they settle. |
| Temperature | 75–82°F (24–28°C). |
| pH | 8.1–8.4. |
| Specific gravity | 1.023–1.026 (reef-standard ≈35 ppt). |
| Other targets | Softies are forgiving — they don't need the high, stable alkalinity/calcium stony corals demand, and they tolerate higher nutrients than SPS. Keep it stable. |
| Feeding | Mostly photosynthetic (light-powered); they'll also catch tiny foods, and occasional fine coral food can boost growth — but light is the main driver. |
| Growth & spread | Fast-growing and collectible — colonies spread across the rock. Easy to frag (with the safety precautions above). |
| Natural range | Indo-Pacific reefs (shallow, high-light zones). |
The fish store gets these wrong
Common myths, kindly corrected — no shame for having believed them.
- “Palytoxin is just scaremongering.” It isn't — there are documented poisonings from boiling and scraping zoa rock. The everyday risk is low; the handling risk is real. Gloves, eye protection, and never boil rock with zoas.
- “Zoas that won't open are dying.” Usually not — closed zoas are most often reacting to too much flow, too much new light, or a pest (check for zoa-eating nudibranchs). Fix the cause and they reopen.
Before you buy
- Get gloves and eye protection FIRST — you'll need them to handle zoas safely.
- Start them low in the tank and acclimate to light slowly.
- Dip and inspect new frags for pests (nudibranchs) before adding.
- Give low-medium flow so the polyps can open.
Signs something's wrong
A struggling coral is almost always telling you about light, flow or water — here's what to watch for:
- Polyps staying closed for days — check flow (too strong?), recent light changes (too much, too fast?) and water quality.
- White pimples on the mat (“zoa pox”), or melting/receding tissue.
- Pests: zoa-eating nudibranchs (camouflaged to look like the zoas), sea spiders, or tiny snails — dip and inspect new frags.
- A whole colony rapidly “melting” — remove affected pieces (gloves!) and check parameters.
Never
- Never boil, scrape or “cook” rock that has zoas on it — this is the classic palytoxin-poisoning scenario.
- Never handle or frag zoas bare-handed or near your eyes/face.
- Never blast them with high flow (they'll stay shut).
- Never add a new frag without checking it for pests.
Common zoanthids questions
Are zoanthids dangerous, and what is palytoxin?
Some zoanthids and Palythoa carry palytoxin, a potent toxin that's a danger to the keeper (not the tank). It's held in the coral's flesh, so simply having them is low-risk — the danger comes from damaging a colony: fragging, scraping, and especially boiling rock with zoas on it. Always wear gloves and eye protection, never boil zoa rock, and seek medical help if exposed.
Why won't my zoanthids open?
Most often it's too much flow, too much new light too quickly, or a pest. Move them to low-medium flow, acclimate to bright light over several days, and check closely for zoa-eating nudibranchs. Fix the cause and they reopen.
Are zoanthids good beginner corals?
Yes — they're hardy, forgiving, fast-growing and come in endless colours. The only thing that sets them apart from other beginner corals is the palytoxin handling caution, not their day-to-day care.
What lighting and flow do zoanthids need?
Low-to-moderate light (roughly 75–250 PAR, acclimated slowly) and low-medium flow — enough to keep detritus off the polyps without blowing them closed.
Do I need to feed zoanthids?
Not really — they're mostly light-powered. They'll catch tiny foods, and occasional fine coral food can help growth, but good light is the main driver.
Sources & further reading
This guide was written and fact-checked against these authorities. It's honest, general guidance — not a diagnosis, and not a substitute for an aquatic vet or your own test kit:
- Bulk Reef Supply — Zoanthid Coral Care Guide — lighting/PAR, flow, placement, difficulty, pests
- Bulk Reef Supply — Zoanthid & Palythoa: Paly Toxin & Fragging — palytoxin safety, fragging
- Tidal Gardens — Zoanthus Coral Care — care + troubleshooting
Written and fact-checked by The Coralkin Team against marine-aquarist sources — if your zoanthids is struggling, it's almost always a light, flow or water-chemistry issue — check those first and ask an experienced reefer. We never guess a care number.
🔬 Review status: team-written and fact-checked against cited sources · not yet reviewed by a marine vet. How we research & fact-check →