Zoanthid and Palythoa Care Guide
Zoanthids are one of the most rewarding corals you can keep. They come in endless color combinations, grow steadily, and adapt to most reef tanks. This guide covers what they need, what goes wrong, and how to handle them safely.
Zoanthids vs. palythoa
Both are colonial polyps from the same family. Zoanthids (zoas) have smaller polyps, usually under half an inch, with bright, contrasting colors. Palythoa (palys) have larger polyps, often an inch or more, with more muted colors. Palys usually grow faster and can carry higher levels of palytoxin.
Lighting
Most zoanthids do best under moderate light, roughly 100 to 250 PAR. Too much light can bleach colors or keep polyps closed. Too little turns many morphs brown. When adding a new colony, start it low in the tank and move it up over 1 to 2 weeks if it stays open.
We keep our PAR around the 100-150 range so a wide variety of zoas can benefit during the photosynthesis period.
Flow
Aim for moderate, indirect flow. It should keep detritus off the polyps without folding them over. Strong direct flow keeps zoas closed, and very low flow lets debris settle on them.
Placement
The lower to middle rockwork suits most zoas. They spread across rock over time, so leave space between them and slower corals. Keep them away from aggressive LPS like hammers, whose sweeper tentacles can reach several inches.
Water parameters
Zoas tolerate a range of conditions, but steady parameters bring out the best color. Keep nitrate and phosphate detectable rather than at zero. Zoas in ultra-low-nutrient tanks often shrink or stay closed.
Feeding
Zoanthids get most of their energy from light, so feeding is optional. Many reefers spot-feed small foods like reef roe or powdered coral foods once or twice a week to speed growth.
Common pests
- Zoa-eating nudibranchs: small, well-camouflaged slugs that match the polyp color. Look for clusters of eggs on the colony.
- Sea spiders: thin-legged pests that feed on polyps, often hiding between them.
- Sundial snails: small, flat spiral snails that eat zoa tissue.
- Zoa pox: white pimple-like spots on the stalks, often linked to stress or bacteria.
Dipping every new colony before it goes in your tank catches most of these. See our guide on acclimating and dipping new corals.
Click here: Coral Acclimation & Dipping Guide
Why are my zoas closed?
Common causes include a sudden light change, flow that's too strong, a parameter swing, pests, or a fish nipping at them. New colonies often stay closed for a few days while they adjust, which is normal. For a full checklist, read Why Is My Coral Closed Up?
Handling zoanthids safely
Many zoanthids and palythoa contain palytoxin, a toxin that can cause serious illness through skin cuts, the eyes or inhaled spray.
- Wear gloves and eye protection when handling or fragging them.
- Never frag with open cuts on your hands.
- Never boil, scrub or pressure-wash rock covered in zoas or palys.
- Wash your hands and tools afterward.
Growing a zoa garden
A zoa garden is a section of rockwork covered in different morphs. Place colonies a little apart and let them grow toward each other. Fast growers will overtake slower ones, so group similar growth rates together.
Browse our zoanthid collection to start or expand your garden. All zoa rock garden colonies are shown as WYSIWYG.
