Zoanthids Care Guide for Reef Tanks | Myreeflog

Introduction to Zoanthids

Zoanthids are among the most colorful, forgiving, and fast-growing corals in the hobby. Often simply called "zoas," they come in endless morphs like Rasta, Eagle Eye, Sunny D, Purple People Eater, Bam Bam, Armor of God, Utter Chaos, and Radioactive Dragon Eye. Each morph can differ in pattern and growth rate, yet most share similar care needs that make them ideal for building vibrant zoa gardens on rocks or islands.

In the wild, zoas inhabit shallow reef zones and rely on a combination of photosynthesis and dissolved nutrients to thrive. In aquariums, they respond well to stable parameters, moderate light, and random flow. They also tolerate a wider nutrient range than many corals, which makes them accessible for newer reef keepers. For tracking the steady conditions zoanthids prefer, tools like My Reef Log help you log tests, visualize trends, and catch drifts before polyps start closing or shrinking.

While commonly grouped together, there are differences between Zoanthus (typically smaller polyps and tighter mats) and Palythoa or Protopalythoa (larger polyps, often thicker tissue). Care is largely similar, with larger polyp palys generally tolerating slightly higher nutrients and lower light.

Ideal Water Parameters for Zoanthids

Zoanthids are resilient, but they flourish with consistent parameters and non-zero nutrients. Aim for these ranges:

Temperature: 77 to 79 F (25 to 26 C)
Salinity: SG 1.025 to 1.026 (35 ppt)
pH: 7.9 to 8.3
Alkalinity: 7.5 to 9.0 dKH
Calcium: 380 to 450 ppm
Magnesium: 1280 to 1400 ppm
Nitrate: 5 to 20 ppm, many zoas color up best around 10 to 15 ppm
Phosphate: 0.03 to 0.10 ppm, avoid truly zero readings

Zoas tend to sulk or "melt" in ultra low nutrient systems. If nitrate is below 2 ppm and phosphate is undetectable, feed more, reduce export slightly, or increase bioload with a small fish. If nitrate exceeds 25 ppm or phosphate rises above 0.15 ppm, gradually increase export through larger water changes, enhanced media such as GFO or PhosGuard, and improved refugium lighting. For deeper dives, see Nitrate in Reef Tanks: Complete Guide | Myreeflog and Phosphate in Reef Tanks: Complete Guide | Myreeflog.

Magnesium stabilizes alkalinity and calcium, and it supports smoother growth and less nuisance algae on zoa mats. If your magnesium is chronically low, correct it slowly over several days to avoid stressing the colony. Learn more in Magnesium in Reef Tanks: Complete Guide | Myreeflog. Temperature stability is equally important, especially during seasonal changes, so confirm your heater and fan controllers hold steady values. If you see swings larger than 2 F day to night, review Temperature in Reef Tanks: Complete Guide | Myreeflog.

Consistency beats perfection. Record test results weekly, then chart them to confirm trends. With My Reef Log, you can set alert thresholds for nitrate or phosphate so you are notified when values drift outside your preferred range.

Lighting Requirements for Zoanthids

Zoanthids adapt to a wide range of light, but most morphs are happiest in moderate PAR.

PAR target: 80 to 150 at the colony. Larger palys often tolerate 60 to 120, while some high end Zoanthus morphs color up around 120 to 180.
Spectrum: Strong blue channels enhance fluorescence. Peak between 420 to 460 nm brings out the best in greens, oranges, and reds. A balanced spectrum with UV and violet channels improves overall health.
Photoperiod: 8 to 10 hours total is typical for mixed reefs, with 1 to 2 hours of ramp up and ramp down for acclimation comfort.

Acclimation is critical. If moving zoas to brighter zones or upgrading lights, reduce intensity by 20 to 30 percent and slowly increase 5 percent per week while observing polyp extension. Pale tissue, tight stalks, or retracted polyps indicate too much light. Extended stalks reaching up, dull coloration, or slow growth often signal light is too low.

Many reefers keep their zoa gardens on lower rock shelves and gradually move frags upward after 2 to 4 weeks of observation. Logging PAR readings or light settings and noting polyp behavior in My Reef Log helps you fine tune your peak blue percentages without guessing.

Flow Requirements

Random, moderate flow is best. Aim for polyp skirts to gently sway without folding or blowing backward. Too little flow allows detritus to accumulate on the mat, encouraging film algae. Too much flow keeps polyps closed and can detach fresh frags.

Tank turnover: 20 to 30 times per hour is a good baseline for mixed reefs.
Pump mode: Gyre or random pulse patterns create suitable turbulence without a harsh laminar blast.
Signs of insufficient flow: Dusty mat, micro bubble accumulation, cyanobacteria creeping between polyps.
Signs of excessive flow: Polyps closed most of the day, skirts pinched, sand kicked up on the colony.

Place zoa colonies off direct pump output, ideally in the lee of rock where the flow is diffused. Rotate pumps slightly each week to prevent dead spots on the mat.

Feeding Zoanthids

Zoanthids derive a large portion of their energy from zooxanthellae, but they benefit from dissolved nutrients and fine particulate foods. In tanks with very clean water, supplemental feeding improves growth and keeps colors rich.

Particle size: 50 to 200 microns. Products like reef powders, rotifers, and fine copepod blends work well.
Schedule: Broadcast feed 1 to 2 times per week. Target feeding is optional for larger palys using a pipette with the flow briefly reduced.
Amino acids: Low dose amino supplements can enhance extension and coloration, use sparingly to avoid fueling nuisance algae.
Timing: Feed when polyps are open, often near the end of the light cycle or shortly after lights ramp down.

If you notice film algae after feeding, reduce the amount or increase export a bit. Look for sustained polyp extension and new heads forming at the edges within a few weeks of a consistent feeding routine.

Placement and Compatibility

Zoas are not aggressive stingers, but they can overgrow neighboring corals if given time. Plan islands or isolated rocks, then trim the mat periodically as heads creep across bare surfaces.

Placement: Lower to mid levels are ideal, on stable rock with moderate light and flow. Frag racks are helpful during quarantine and acclimation.
Spacing: Keep at least 2 inches away from slower growing LPS to prevent overgrowth. Some morphs spread rapidly, so maintain a pruning schedule.
Tankmates: Compatible with most reef-safe fish like clownfish, gobies, wrasses, and blennies. Avoid butterflyfish and many angelfish that may nip polyps. Keep an eye on crabs that pick at mats.
Invertebrates: Snails and cleaner shrimp are generally safe. Watch for sundial snails or predatory spiders that specifically target zoas.

Safety first. Some Palythoa and Protopalythoa can contain palytoxin. Wear nitrile gloves and eye protection when fragging or scrubbing mats, keep tools separate from kitchen items, and avoid aerosolizing tissue with hot water or power tools.

Common Issues and Solutions

Pests and Predators

Zoa-eating nudibranchs: Look for frilly, polyp-colored nudis on the underside of heads and on nearby plugs. Remove adults with tweezers, scrape egg clusters, and perform dips. Lugol's iodine dip can be used at 15 drops per liter for 5 to 10 minutes, then rinse in clean saltwater. Repeat every 3 days until no nudis or eggs are observed.

Sundial snails and zoa spiders: Inspect at night with a flashlight. Manually remove pests and consider a series of iodine dips. Quarantine new frags for 2 to 3 weeks to prevent reintroduction.

Disease and Melting

Zoa pox: Small white pustules on the stalks often respond to Furan-2 dips. Use approximately 1 packet (250 mg) dissolved in 1 cup of tank water, dip for 15 to 20 minutes once per day for 2 to 3 days, then allow a recovery period. Maintain stable nutrients during treatment.

Bacterial films: Improve flow, reduce feeding, and siphon detritus around the mat. Brief hydrogen peroxide dips are sometimes used, but proceed carefully. If you try it, keep it conservative at 1 part 3 percent peroxide to 10 parts tank water for 3 to 5 minutes, then rinse well. Observe polyps closely afterward and avoid repeated use.

Light and Nutrient Stress

Bleaching or pale tissue: Too much light or too little nutrients. Reduce light intensity by 20 to 30 percent and bring nitrate up to 5 to 10 ppm, phosphate to 0.03 to 0.07 ppm.

Persistent closed polyps: Check for pests first, then review flow and parameters. Confirm alkalinity is stable day to day within 0.3 dKH, and verify temperature does not swing more than 1 to 2 F. If phosphate is truly zero, increase feeding or reduce export slightly.

Algae overgrowth on the mat: Increase flow, manually brush off with a soft toothbrush, and reduce light photoperiod by 1 hour for 2 weeks. Bring nutrients into a balanced range rather than driving phosphate to zero.

Tips for Success

Start with hardy morphs like Eagle Eye, Radioactive Dragon Eye, Bam Bam, or Scrambled Eggs. They tend to tolerate a wider range of light and nutrients.
Quarantine and dip new frags. A 5 to 10 minute iodine dip followed by careful inspection under white light catches most hitchhikers.
Build a zoa island. Use an isolated rock in the sand to keep rapid growers from overrunning your aquascape. Prune the mat monthly.
Keep nutrients non-zero. Target nitrate around 10 to 15 ppm and phosphate around 0.05 ppm. Adjust export slowly to avoid sudden swings.
Stabilize alkalinity. Daily swings larger than 0.3 dKH stress polyps. If you dose, spread additions across the day or use a doser to automate small increments.
Track your light. Note PAR and blue channel percentages when you see color improvements or setbacks. Record these observations in My Reef Log so you can reproduce success.
Handle safely. Wear gloves, use dedicated coral tools, and rinse work areas. Do not boil rock containing palythoa.
Encourage biodiversity. A small refugium, regular feeding, and clean RODI water with TDS under 2 support a stable micro environment for zoa mats.
Use reminders and logs. Set monthly frag maintenance and quarterly pest inspections. My Reef Log reminders reduce the chance of skipping small but important tasks.

Conclusion

Zoanthids offer stunning color, manageable care, and rapid growth that rewards patient reef keepers. With steady parameters, moderate light, random flow, and a practical feeding routine, even modest systems can produce dense, vibrant colonies. Keep nutrients balanced, inspect for pests, and adjust light gradually. If you document your changes and watch for trends with My Reef Log, you will refine your approach and keep your zoa garden flourishing for years.

FAQ

Are zoanthids good for beginners?

Yes. Zoanthids tolerate a wider nutrient range than many corals, they grow quickly, and they adapt to moderate light and flow. Start with hardy morphs and keep nitrate and phosphate non-zero to avoid melting.

What PAR should I target for zoanthids?

Most morphs thrive at 80 to 150 PAR. Larger palys often do well at 60 to 120, while some higher end Zoanthus color up best around 120 to 180. Acclimate slowly and observe polyp extension.

How do I get zoas to spread faster?

Keep nitrate around 10 to 15 ppm, phosphate near 0.05 ppm, maintain alkalinity stability, and provide moderate flow. Broadcast feed fine particulate foods 1 to 2 times weekly and avoid harsh light increases.

What pests should I watch for?

Zoa-eating nudibranchs, sundial snails, and zoa spiders are common. Quarantine new frags, perform iodine dips, and inspect under white light. Remove eggs and repeat dips until clear.

Can zoanthids harm me?

Some Palythoa and Protopalythoa can contain palytoxin. Wear gloves and eye protection when handling or fragging, avoid aerosolizing tissue, and keep tools separate from household items.