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Zoanthids, or "zoas", are one of the most colourful and collectable corals you can keep. They are small polyps that spread across rock to form a living carpet, and there are hundreds of named varieties to choose from. Most are hardy and grow well in a wide range of reef tanks. This guide covers how to keep zoanthids and palythoa healthy, how to handle them safely and how to fix the most common problems.
Quick facts
| Coral type | Soft coral (colonial polyps) |
| Care level | Easy |
| Lighting | Low to high, roughly 50 to 200 PAR (around 100 to 150 suits most) |
| Flow | Moderate |
| Placement | Anywhere from the sand bed to the middle of the rockwork |
| Temperament | Peaceful, but can spread over neighbouring corals |
| Safety | Some species, especially palythoa, contain palytoxin. Wear gloves and eye protection when handling them |
Zoanthids vs palythoa
Zoanthids (Zoanthus) have small polyps, usually under 1cm across, and come in the widest range of colours and patterns. Varieties such as Rasta, Utter Chaos and Bam Bam are collected and traded by name.
Palythoa ("palys") have larger polyps and often grow faster. They are very hardy, but they generally contain more palytoxin, so take extra care when handling and fragging them.
Shop our full range of zoanthids and palythoa, including WYSIWYG colonies and "zoa gardens" with several varieties on one rock.
Handle zoanthids safely
Palytoxin is a strong toxin found in some zoanthids and palythoa. Problems are rare with sensible precautions, but they can be serious, so always:
- Wear gloves and eye protection when handling, cutting or fragging zoas and palys.
- Never boil, scrub or pressure-wash rock with zoanthids on it, and never dry it out with a heat gun, as this can release toxin into the air or spray it into your eyes.
- Wash your hands after working in the tank, and keep cuts covered.
- Seek medical advice if you feel unwell after handling them.
Water parameters
- Temperature: 24 to 26°C
- Salinity: 1.025 to 1.026 SG (about 35ppt)
- Alkalinity: 7 to 9 dKH
- Nitrate: 2 to 10ppm
- Phosphate: 0.03 to 0.1ppm
Zoanthids are forgiving, but they don't like water that is too clean. If nitrate and phosphate drop to zero, polyps often shrink, stay closed or "melt". Keep a little nutrient in the water. Our guide to phosphate in a reef tank explains how to find the right balance.
Lighting
Most zoanthids grow well at around 100 to 150 PAR, and many show their best colours there. Some varieties prefer less light and some tolerate much more. If the polyps stretch tall on long stalks, they want more light. If they stay small, pale or half-closed, the light may be too strong. As with any coral, start low and move it up gradually. A PAR meter makes this easy.
Flow
Moderate flow keeps detritus off the polyps and helps them feed. If waste settles on the colony, the polyps may stay closed. If the polyps are bent flat, turn the flow down a little.
Placement
- Zoas spread outward over the rock. Put them where they can grow without covering slow-growing corals.
- Different varieties can grow into each other. To keep a collection separate, mount each one on its own frag plug or on a display piece such as the Charterhouse 3D Zoa Flower.
- Fix plugs and frags with Seachem Reef Glue or Reef Zlements Gel Frag Glue.
Feeding
Zoanthids get most of their energy from light. They will also take fine foods, which can help growth in tanks with very low nutrients. Feed lightly once or twice a week with a fine coral food such as Aquaforest AF Zoa Food, or browse our coral foods.
Common problems
Zoas not opening
Check for recent changes in salinity, alkalinity or lighting, and for detritus or algae on the colony. Check for pests too: look at the base of the polyps with a torch after lights out, and watch for fish or crabs picking at them.
Zoa pox
Zoa pox shows up as small white pimples on the polyp stalks, usually on stressed or newly imported colonies. Keep water quality high and stable, and use a coral dip to help the colony recover. Treat affected frags in a separate container so the pox doesn't spread.
Zoa-eating pests
Zoa-eating nudibranchs, sea spiders and small snails can wipe out a colony. Dip every new zoanthid before adding it to your display, using a dip such as Coral Rx Pro or Seachem Reef Dip, and check the base and underside for eggs. Our coral dipping guide explains each step.
Polyps melting or disappearing
This is usually down to very low nutrients, a sudden lighting change or pests. Test nitrate and phosphate first, then check for pests.
Fragging zoanthids
Zoanthids are among the easiest corals to frag. Wearing gloves and eye protection, cut through the mat between polyps with a sharp scalpel or propagation tools, keeping a few polyps per frag. Glue each frag to a plug. They usually reattach and open within a few days. Read more in our coral fragging guide.
Frequently asked questions
Are zoanthids good for beginners?
Yes. Most zoanthids and palythoa are hardy and tolerate a wide range of conditions, which makes them one of the best first corals. See our 12 easiest corals for beginners.
How fast do zoanthids grow?
It depends on the variety. Some double in a few months, while some rarer types are much slower. Palythoa usually grows faster than Zoanthus.
Why are my zoas closed during the day?
The most common causes are a recent parameter swing, too much or too little light, detritus on the colony, or pests. Work through the checks in the common problems section above.
Are zoanthids dangerous?
They are safe to keep in a reef tank. The risk comes when you handle or frag them, so follow the safety advice above.
Shop zoanthids and palythoa
Browse our full range of zoanthids and palythoa, from affordable starter frags to collector colonies. For more soft coral advice, read Soft Corals Explained.
