Quick Notes about Zoanthids
| Name | Zoanthid corals (Zoas, Button Polyps) |
| Scientific Name | Zoanthus sp. / Palythoa sp. |
| Tank size (min) | 10 gallons (~40 liters) |
| Keeping | Easy to Moderate |
| Optimal Temperature | 75 – 80°F (24 – 27°C) |
| Optimal Salinity | SG = 1.025 |
| Optimal pH | 8.1 – 8.4 |
| Optimal KH | 8 – 12 dKH |
| Nitrate | 5 – 10 ppm (Do not chase 0) |
| Lighting (PAR) | 100 – 250 (Moderate) |
| Water flow | Medium, indirect |
| Toxicity | High in some species (Palytoxin) |
Background Information and Natural Habitat
Here’s the thing about zoas — they’re survivors. In the wild, they live in intertidal zones where they get baked by the sun at low tide, frozen by cold fronts, and smashed by waves. Think about that. These things get exposed to air, rain, and blazing sun, and they just… shrug it off. That’s why they’re so tough in your tank.
Key characteristic: They do this weird thing where they trap sand grains in their body wall (the coenenchyme). It’s like they’re building their own concrete. Makes them structurally strong. They reproduce two ways: sexually (free-swimming larvae that settle somewhere new) or asexually (budding, where the colony just spreads). Most of the zoas you buy are clones from budding.
Description of Zoanthid Genera: What Does Each Type Look Like?
Palythoa
These are the DANGEROUS ones!
They look like regular zoas (pale yellow, brown, or sometimes vibrant green/orange), but the polyps feel thicker, almost leathery.
In the wild, they form massive colonies on reef flats — we’re talking several meters across. In your tank? Keep them away from expensive SPS corals.
⚠️ Warning: Why? Palytoxin. It’s lethal. Wear gloves when handling them. Seriously.
Protopalythoa
These are the GIANTS. Polyps can reach 1-2 inches across — bigger than most zoas you’ll see.
Thick, slimy tissue with sand embedded in the lower columns. Usually brownish with green oral discs, sometimes striped or mottled. They live on reef slopes and sandy flats in the wild, from shallow to deep water.
Aquarium care: High lighting, strong flow. Feed meaty foods: shrimp, worm flesh, mollusk, fish eggs, flakes.
⚠️ Warning: Highly toxic mucus that destroys scleractinian coral tissue. Never place near SPS.
Zoanthus
These are the PRETTY ones.
Contrasting shades of green/brown, red, orange, pink, blue, yellow, lavender, grey — usually two-toned. They form densely crowded mats or branched stolon-like bases. These are your Fire & Ice, Sunny D, Blue Hornet — the classic “zoas” everyone keeps.
Why they’re tough: In the wild, they live in intertidal zones — exposed to air, sun, and rain at low tide. They’ve evolved to take a beating.
Aquarium care: Moderate to strong lighting. Feed mysis, brine shrimp, flake foods.
Acrozoanthus
Large brown polyps with very long, stringy tentacles. They look like they’re reaching for something. Docile and adaptable — they don’t fight with tankmates.
Aquarium care: Strong illumination. Feed marine copepods and thawed meaty foods.
Note: Rarely available in local fish stores. Most Acrozoanthus you find are wild-collected.
Isaurus (Snake Polyps)
Weird little guys.
Elongated columns with bumps, oriented so the ends face downward. Three valid species: I. tuberculatus, I. cliftoni, I. maculatus. They look like snake skin — hence the name.
Aquarium care: Feed marine copepods, artemia, and brine shrimp nauplii.
Feeding Zoanthids: The Photosynthesis Trap
Well, zoas won’t die if you only give them light. They’ve got zooxanthellae (symbiotic algae) that turn light into energy. But here’s the catch — they’ll survive, not thrive.
Want neon colors? Fast growth? Polyps that stay open 24/7? You gotta feed them.
The Target Feeding Protocol:
- Turn off your powerheads and wavemakers. If the water’s moving, your food blows away before the polyps can grab it.
- Mix phytoplankton or frozen mysis in a cup of tank water.
- Grab a turkey baster (or syringe) and squirt the mix directly onto the colony.
Watch what happens — healthy polyps will fold inward and open their mouths like little vacuum cleaners. - Wait 15 minutes, turn the flow back on. Done.
What to Feed Them
- Phytoplankton (Liquid): The absolute gold standard for daily/weekly maintenance. It brings out the best coloration, especially in blue and green morphs. See our guide on how to culture phytoplankton if you want to save money.
- Frozen Mysis or Brine Shrimp: Thaw it first. Great for bulk growth. Don’t use it exclusively — it’s too heavy and will spike your phosphates if you overfeed.
- Reef Roids / Polyp Booster: Fine powder that triggers a massive feeding response. Use sparingly. A little goes a long way.
- Marine Zooplankton: Frozen marine zooplankton from your local fish store. Expensive, but if you want premium nutrition, this is it.
Tank Requirements: Water Parameters That Actually Matter
Zoas are forgiving, but they hate swings. Stability is your actual goal. I’ve seen colonies survive in tanks with mediocre parameters as long as they were stable. But the moment you start chasing perfect numbers and changing things daily, they’ll melt.
The Critical Parameters
- Temperature: 75 – 80°F (24 – 27°C). Above 82°F, they will bleach. Below 72°F, polyp expansion slows dramatically. Get a reliable heater with a thermostat. Don’t trust the dial on cheap heaters — use a separate thermometer.
- Salinity: 1.025 SG. Use a glass refractometer, not a plastic hydrometer. Those are garbage and will kill your corals. I’ve watched beginners lose entire colonies because they trusted a $5 plastic arm that was off by 0.003.
- pH: 8.1 – 8.4. Below 7.8, they start losing color. Above 8.5, you’re dosing too much buffer.
- Alkalinity (KH): 8 – 12 dKH. Keep it stable. Don’t chase a specific number. If it’s bouncing between 6 and 14, your corals will stress.
- Nitrates (NO3): 5 – 10 ppm. Do not chase zero nitrates. Zoas are filter feeders; they need a tiny bit of nitrate to sustain their color and growth. If you’re running a ULNS (ultra-low nutrient system) for SPS, your zoas will turn brown and lose vibrancy.Phosphates (PO4): Below 0.03 ppm. High phosphates will kill their color and invite algae. But don’t go to zero — you need a tiny bit for the zooxanthellae. Check our guide on phosphates in reef tanks.
Follow the dosage instructions on your specific iodine supplement bottle. Overdosing is worse than underdosing.
Lighting (PAR Requirements)
Most zoas need moderate light (PAR 100–250).
If you put them directly under a high-end LED on full blast, they will bleach white in 48 hours. If you put them in the dark shadows, they will stretch, lose color, and eventually die.
Note: If you don’t have a PAR meter, place your zoas in the middle third of your tank. If they stretch up (looking for light), move them higher. If they bleach, move them lower. Acclimate them slowly over 2-3 weeks. Don’t rush this.
Here’s the reality: most “moderate light” corals die because people either blast them with 400 PAR or stick them in a corner with 30 PAR. There’s a sweet spot, and you find it by watching the coral’s response. If the polyps are fully extended and colorful, you’re good. If they’re closed or bleached, adjust.
Water Flow & Placement
Place them in medium, indirect flow.
They need enough flow to blow detritus off their mats, but not so much that their polyps stay retracted 24/7. Never point a powerhead directly at a zoa colony. Bottom-to-middle placement is usually the sweet spot.
Pro tip: If your zoas are constantly closed, check your flow first. Too much current is the #1 reason they won’t open. I’ve seen people chase lighting and water parameters for weeks when the problem was a powerhead blasting the coral directly. Move it 6 inches away and watch them open up overnight.
Zoas Closed Up? Run This Checklist.
If your zoas are closed for more than a day, something’s wrong. Don’t panic — run through this list:
- Flow too strong? Move the colony 6 inches (15 cm) away from the powerhead. If they open, you found the problem.
- Light too intense? Bleached or closed? Move them down an inch per day until they open.
- Nitrates at zero? They need 5–10 ppm. Zero nitrate tanks produce brown zoas that never open fully.
- Iodine deficiency? Colors fading? Dose Lugol’s once a week and watch them perk up.
- Pests? Check for nudibranchs, sundial snails, or sea spiders. If you see them, dip immediately.
If none of these fix it, check your salinity and pH. But 80% of the time, it’s flow or light.
Care and Maintenance: The Weekly Routine
Generally, caring for Zoanthids is very easy. It’s one of the few corals that can thrive successfully in most reef tanks. But “easy” doesn’t mean “no maintenance.” Here’s what you need to do:
Weekly Checklist
- Check polyp expansion (should be open 80%+ of the time). If they’re closed, something’s wrong — flow, lighting, or water parameters.
- Look for closed polyps or white spots (early disease signs). Catch problems early before they spread.
- Dose iodine if needed. If you notice color fading, add Lugol’s solution.
- Target feed once per week. Don’t skip this if you want vibrant colors.
- Check for pests (nudibranchs, sundial snails). They can decimate a colony in days if you don’t catch them.
How Often to Change Water
Do a 10–15% bi-weekly water change. If your nitrates climb above 10 ppm, bump it to weekly. Don’t skip water changes thinking you can just dose your way out of problems — iodine and other elements deplete faster than you think.
Monthly Maintenance
Once a month, do this:
- Test your water. Nitrates, phosphates, pH, KH, salinity. Don’t guess — I’ve seen people lose colonies because they “thought” the parameters were fine.
- Clean your powerheads. If they’re clogged, you’ve got dead spots where detritus piles up. Zoas hate that.
- Check for algae on the zoa mats. Cyanobacteria? Kill it now, or it’ll spread.
- And if your zoas are overgrown and shading other corals, frag them.
Related: Top 10 Corals for Beginners
Placement of Zoanthids in Aquariums
Where you put your zoas matters just as much as how you feed them. I’ve seen people blast them with 400 PAR under a powerhead and wonder why they melted in three days. Here is the reality:
- Flow: Medium, indirect flow. You want enough current to blow detritus off the mat, but not so much that the polyps stay retracted 24/7. Never point a powerhead directly at a colony. If they look like they’re hiding, move them.
- Light: Bottom to middle placement. They like light, but if you put them on the sand bed in the shadows, they’ll stretch and lose color. If you put them under a blazing LED, they’ll bleach. Acclimate them slowly over two weeks.
- Spacing: Keep them away from aggressive SPS corals. Some zoas (especially Palythoa) can sting nearby tankmates. Give them their own real estate.
Pro tip: If your zoas are constantly closed, check your flow first. Too much current is the #1 reason they won’t open. Move them six inches away from the powerhead and watch them open up overnight.
Fragging and Propagation Zoanthids
In the wild, these polyps reproduce by sexual reproduction (free-swimming larvae) or asexual budding. In your tank, you’re going to propagate them by fragging.
You can propagate a zoa by cutting it together with the live rock it is attached to. For this exercise, you can utilize a dremel, precision knife, scalpel, stony coral cutter or band saw.
Once the polyp has been split, you can glue it to a frag plug or disc with a cyanoacrylate gel or super glue gel before putting it back into the tank.
⚠️ Palytoxin can cause serious harm. I’m not joking. Some zoas (especially Palythoa) contain palytoxin — it can be absorbed through your skin, and if it gets in your eyes or bloodstream, you’re looking at a hospital visit. Or worse.
Always wear nitrile gloves. Always. Even if you are just moving a frag. And safety goggles when cutting! After handling zoas, wash your hands with soap and water. Even if you wore gloves. Better safe than dead.
Tools You Will Need
Depending on your method, you’ll need a few specific tools to get the job done without destroying the colony:
- A hammer and chisel: For splitting live rock if the zoas are encrusted.
- Scissors or a scalpel: For cutting the mat itself if you’re fragging a thick colony.
- Cyanoacrylate glue (gel): Regular super glue works, but the gel version won’t run everywhere in the water.
- Coral frag disks or plugs: To glue the new frag onto.
- A container of tank water: To dip the frag in while you work (keeps the tissue from drying out).
Problems Associated with Zoanthids
There’s quite a number of diseases and pests that can wreck your zoanthids. If you catch them early, you can save the colony. If you ignore them, you’ll lose the whole tank.
Zoa Pox
Zoanthid pox is a disease that affects zoanthids, and the exact cause is still unknown. It manifests by forming small yellowish or white marks on the outside stalks. Eventually, the affected polyps will gradually close up and get covered with the pox. If left untreated, the sick polyps will decline and die.
This infection can be cured using Furan-2, following these steps:
- Empty 1 packet of Furan-2 into a cup of tank water (match the salinity to your tank).
- Stir thoroughly until it is completely dissolved.
- Put affected zoas in the mix and soak for 15 to 30 minutes.
- Repeat treatment once daily for 3 consecutive days.
- Rinse the zoas with tank water in a separate container to get rid of residue.
- Place the zoas back into the tank, preferably in areas with strong flow.
- Allow them to rest for 4-7 days. If the pox persists, do another series of treatments (reduce dipping time to 10 minutes).
Note: Some aquarists dip infected Zoanthid corals into freshwater. Although Zoanthids are pretty hardy, I do not recommend this method. Also, do not confuse sand irritation with Zoa pox.
White Fungus (White Death)
White fungus looks like a cotton film. If left untreated, the corals will die or melt away. Nobody really knows the exact cause, but the most popular theory says it’s due to a lack of water motion or an accidental injury to the coral.
Possible treatments include Lugol’s solution, hydrogen peroxide, Maracyn 1, and Furan 2.
- Lugol’s solution: 300 ml of tank water with 3–5 drops of Lugol’s for 3 minutes.
- Hydrogen peroxide: Slowly add it until you see bubbles forming around the base. Let it bubble for 5 minutes. Take a soft paintbrush and gently rub between the polyps. Then dip them into a weak solution of Lugols or Furan 2. Repeat for a week.
Warning: Do not use any of these treatments in the main tank. It is only for dipping in a separate container.
Bleaching and Dark Stems
Bleaching: This happens when zooxanthellae are expelled from the coral. The polyps lose their natural color and turn translucent white. It’s caused by extreme lighting, temperature swings, or salinity changes. Fix your parameters immediately or the coral will die.
Dark brown/black stems: This is often a sign of a severe bacterial infection. Use a soft toothbrush to gently scrub the dying tissue away, then dip in iodine diluted saltwater or use Furan-2 treatment.
Hitchhikers: Nudibranchs and Snails
These hitchhikers include zoa-eating nudibranchs, sundial snails, and sea spiders. They feed on zoanthids and may have been introduced to the tank by new corals. They can decimate a colony in days if you don’t catch them.
You can eliminate them by handpicking with tweezers. For a chemical approach, quarantine the zoanthids using CoralRX:
- Add 20 ml of CoralRX (check instructions) to 1 gallon of aquarium saltwater.
- Submerge the zoas and gently shake them in the dip.
- Using a turkey baster, blast the corals with the dip for 5-10 minutes (ensure it gets between the polyps and the underside).
- Rinse with tank saltwater and place back into the tank.
Warning: Chemicals can kill the adults but not the eggs. You have to repeat the treatment in two weeks once they hatch. If nothing helps, use the freshwater method as a last resort. If you dip them in freshwater, do it outside and wear a mask.
Buying and Quarantining Zoanthids
Buying a healthy zoanthid will significantly increase your chances of success. Healthy zoas can be identified by the presence of colorful polyps (not washed-out) and fully extended tentacles. If the tentacles are retracted, the coral is stressed or sick.
Buying a large colony is a waste of money. A small frag with just a few polyps will grow and multiply rapidly under the right conditions. Zoanthids are relatively cheap, so start small and let them spread.
Which Zoas Should a Beginner Buy?
If you’re new to this, skip the toxic stuff. Start with Zoanthus species — they’re the most forgiving. Classic morphs like Fire & Ice, Sunny D, and Blue Hornet grow fast, open wide, and don’t produce lethal palytoxin.
Avoid Palythoa and Protopalythoa until you’ve fragged a few colonies and know how to handle them safely. They’re not harder to keep — they’re just more dangerous. Gloves aren’t optional with those.
Always Dip New Zoas
Even if the frag looks clean, dip it. I don’t care if it came from a “reputable” source — every reefer who’s lost a colony to nudibranchs will tell you the same thing. Use CoralRX or a similar coral dip before quarantine.
Here’s the quick method:
- 5-10 ml (check instructions) CoralRX per gallon of tank water,
- soak for 5–10 minutes,
- blast the polyps with a turkey baster to knock off any hidden pests,
- rinse, and then into quarantine.
Pests are easier to kill in a dip than after they’re embedded in your display rockwork.
Frequently Asked Questions
What do zoanthids eat?
They get most of their energy from photosynthesis, but they need meaty marine foods to grow fast. Target feed them marine phytoplankton, frozen mysis, or reef roids once a week. If you don’t feed them, they’ll survive, but they won’t thrive.
What are the light requirements for zoa corals?
Moderate light. You’re looking at a PAR of 100 to 250. Acclimate them slowly. If you blast them with high-end reef lighting right away, they’ll bleach. If they stay closed up, the light is either too weak or way too strong.
Where is the best placement for zoanthids in a tank?
Bottom to middle. They like medium water flow—enough to blow detritus off their mats, but not so strong that their polyps retract 24/7. Keep them away from aggressive SPS corals.
Are zoanthids toxic to humans?
Some species (specifically Palythoa and Protopalythoa) contain palytoxin, which is highly toxic. It can cause severe illness or death if it enters your bloodstream or eyes. Always wear gloves and goggles when fragging them, and never boil them.
How fast do zoanthids grow?
Under optimal conditions (moderate light, weekly feeding, iodine dosing), a small frag can double in size every 2 to 3 months. If they aren’t growing, check your nitrates and flow first.
Bottom Line
Zoanthids are bulletproof if you don’t overthink them. Keep the tank at 75–80°F, put them in a spot with medium flow and moderate light, and blast them with meaty marine foods once a week. Dose iodine weekly. And for the love of your nervous system, wear gloves when you frag them. Give them the basics, and they will cover your rockwork in color.
Related articles:
- Top 10 Corals for Beginners
- How to Care for Green Star Polyps
- How to Care for Bird’s Nest Corals
- How to Care for Acan Corals
- Proper Care for Carpet Anemone
- How to Care for Torch Corals
- How to Care for Frogspawn Corals
- How to Care for Hammer Corals
- How to Care for Elegance Coral
- How to Care for Bubble Tip Anemones
- How to Care for Pulsing Xenia
- How to Care for Ricordea Coral
- How to Care for Palm Tree Polyp
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Thank you very much for this information! I am crazy about zooanthus and I have a few but I can’t breed them. On the other hand, my polyps are disappearing and I don’t understand why? I separated them from the large tank into a nano but still in vain.. how could I breed them? what parameters do they need? Thank you very much for the information you can give me!
Hi Maciuca Marin,
Sorry your zoas are struggling.
Most likely causes:
1. Predators – sundial snails or zoa-eating nudibranchs. Check at night.
2. Bad parameters – keep salinity 1.023–1.025, temp 24–26°C, nitrate 1–5 ppm, phosphate 0.02–0.08, alk 8–12, calcium 400–450.
3. Too much flow or sudden swings – zoas like low/moderate flow and stability.
Once healthy, you can frag them and glue to a new plug.
Dip a test frag in iodine-based coral dip, remove pests, and keep things stable. They should bounce back.
Best regards,
Michael