Zoanthid corals, or "Zoas," are some of the most vibrant and rewarding soft corals in the marine aquarium trade. Known for their explosive colour variations and hardy nature, they've become a favourite among beginners and advanced reef keepers alike. With hundreds of named morphs and new varieties appearing regularly, Zoanthids offer endless possibilities for aquascaping and coral propagation.
Natural Habitat & Appearance
Zoanthids occur across tropical and subtropical oceans, particularly in the Caribbean, Indo-Pacific, and Red Sea. They typically grow in shallow reefs where water movement and light fluctuate daily. This natural adaptability explains why Zoas can thrive in many aquarium setups.
Polyps are small usually 5–15 mm but form mats that spread across rockwork. Colours range from neon greens and fiery oranges to rare rainbows, with collectors giving morphs names such as "Rastas," "Purple Death," or "Rainbow Incinerators." Colonies expand quickly thanks to a shared base tissue called coenenchyme, giving tanks a striking "carpet" effect when Zoas spread.
Tank Requirements
Lighting
Zoanthids thrive in moderate light, generally 100-200 PAR. Most varieties do best under LED lighting with a spectrum leaning towards blues to enhance fluorescence. Avoid blasting them with intense light; stability and moderation are far more important for growth and colour retention. Many keepers report best results with 8-10 hours of photoperiod, ramping up and down gradually to simulate natural conditions.
Flow
Moderate, indirect flow is ideal. Polyps should sway gently without being flattened. Random or pulsing flow patterns (using gyres or multiple powerheads) prevent detritus buildup and mimic natural reef conditions. Aim for 10-20x tank volume turnover per hour, distributed across multiple flow sources.
Water Parameters
| Parameter | Recommended Range | Notes |
|---|---|---|
| Temperature | 24–26°C (75–79°F) | Keep stable |
| Salinity | 35 ppt (1.025–1.026 SG) | Consistency is key |
| pH | 8.1–8.4 | Minor daily swings are normal |
| Alkalinity | 7–10 dKH | Keep steady, avoid big swings |
| Calcium | 400–450 ppm | Supports healthy tissue and growth |
| Magnesium | 1300–1500 ppm | Helps stabilise Ca/Alk balance |
| Nitrate | 2–15 ppm | Slight nutrients encourage growth |
| Phosphate | 0.03–0.1 ppm | Avoid ultra-low levels (risk of bleaching) |
Stable parameters matter more than perfection. Small, frequent adjustments are safer than sudden corrections. Test weekly and maintain consistent water change schedules - 10-20% weekly changes work well for most systems.
Placement in the Aquarium
Place Zoanthids in low to mid-level areas with moderate light and flow. Avoid sand beds (where they may get buried) and direct blast zones near powerheads. Allow space between colonies fast-growing Zoas can quickly encroach on neighbours.
Consider growth patterns when planning placement: aggressive spreaders like Green Bay Packers need isolation zones, whilst compact growers like Armor of God can be placed closer to other corals. Porous live rock provides ideal anchoring surfaces and natural boundaries to contain spreading colonies.
Feeding & Nutrition
Zoanthids contain symbiotic zooxanthellae and can survive on light alone, but targeted feeding accelerates growth and enhances colour. Suitable foods include:
- Phytoplankton
- Finely chopped mysis or brine shrimp
- Cyclops or reef-specific powdered foods
- Amino acid supplements
- Coral-specific liquid foods
Feed 2–3 times weekly, either via broadcast or target feeding with a pipette. Evening feeding often produces better results as polyps are naturally more active. Avoid overfeeding, as it degrades water quality and can promote algae growth over coral tissue.
Growth & Propagation
Safety First
Important: Some Zoanthids contain palytoxin, a dangerous compound that can cause severe illness or death. Always frag or handle Zoas with nitrile gloves, eye protection, and good ventilation. Avoid cuts, do not expose them to heat or dry air, and never frag in enclosed spaces. Work underwater when possible to minimise aerosol formation.
Propagation Techniques
Frag Zoas by carefully slicing through the mat tissue between polyps using a sharp scalpel or frag saw. Work underwater to reduce aerosol risks.
Allow frags to heal for 24-48 hours before handling extensively. Secure new frags with coral glue or putty to prevent dislodgment from flow or curious tankmates. Zoanthids grow rapidly when water quality and nutrition are stable, with many varieties doubling polyp count within 2-3 months.
Seasonal Growth Patterns
Growth rates often vary seasonally, with many keepers reporting faster expansion during warmer months. Some premium morphs may experience slower growth during winter months, which is normal and not cause for concern.
Common Problems
Pests
- Zoanthid-eating nudibranchs: Small, translucent with distinctive finger-like projections
- Sundial snails: Pyramid-shaped shells, often burrow into colony centres
- Zoanthid spiders: Tiny crabs that feed on polyp tissue
- Solution: Quarantine and dip all new frags using commercial coral dips or iodine solutions
Melting
Often caused by parameter swings, bacterial infections, or exposure to toxins. Improve flow around affected areas, stabilise water chemistry, and consider antibiotic dips for severe cases. Remove affected tissue immediately to prevent spread.
Polyp Retraction
Usually linked to lighting changes, flow issues, chemical warfare from neighbours, or unstable nutrients. Systematic evaluation of tank conditions typically reveals the cause. Carbon filtration can help reduce chemical warfare effects.
Compatibility
With Other Corals
Zoanthids can overgrow slower corals and sometimes release allelopathic chemicals. Leave adequate space (5-10cm minimum) and use activated carbon filtration. Excellent neighbours include other soft corals like Kenya trees, Xenia, and leather corals that can compete effectively.
With Fish
Most reef-safe fish ignore Zoas. Avoid large angelfish and butterflyfish that may nip polyps. Tangs and other herbivores actually benefit Zoanthid health by keeping surfaces algae-free.
With Inverts
Snails, shrimp, and most crabs are beneficial cleanup crew members. However, large hermit crabs may knock loose frags, so secure placement is important. Emerald crabs occasionally graze on polyps if underfed.
Tips for Long-Term Success
- Maintain stable parameters rather than chasing perfect numbers - consistency trumps perfection
- Implement quarantine protocols for all new additions: 2-4 week isolation with observation and preventative dips
- Secure frags properly using coral glue or putty to prevent dislodgment
- Document growth and conditions in a reef journal to track what works best for your system
- Join reefing communities (local clubs, online forums) to access rare morphs, troubleshooting advice, and trading opportunities
- Plan for growth by designing aquascapes with expansion zones and natural barriers
- Use activated carbon regularly to reduce chemical warfare and maintain water clarity
- Maintain equipment consistently with regular pump cleaning and light spectrum monitoring
Quarantine Protocol
New Zoanthid acquisitions should be quarantined for 2-4 weeks in a separate system. This allows observation for pests and diseases whilst permitting gradual acclimation to your main system's parameters. Use this time to dip corals and observe for any health issues.
Conclusion
Zoanthids are hardy, colourful, and rewarding corals that adapt well to different tank sizes, propagate easily, and provide an excellent introduction to coral farming. They represent one of the most dynamic segments of the hobby, with new morphs and colour variations discovered regularly.
With stable conditions, safe handling practices, and thoughtful placement, Zoanthids will flourish into vibrant mats that transform rockwork into living art. Their forgiving nature makes them ideal for beginners, whilst their incredible diversity and propagation potential keep experienced keepers engaged for years.
Whether you're starting with common varieties or investing in premium morphs, Zoanthids offer something for every reef keeper and budget. Their rapid growth and stunning visual impact make them among the most satisfying corals to cultivate successfully.
Frequently Asked Questions
Q: How fast do Zoanthids grow? A: Many varieties produce new polyps every 2–4 weeks under good conditions. Fast-growing morphs can double in size within 2-3 months, whilst premium varieties may grow more slowly but steadily. Growth rates often increase with stable parameters and regular feeding.
Q: Do Zoanthids need dosing? A: Not specifically, but stable calcium, magnesium, and alkalinity levels indirectly support growth. Trace elements and amino acids can improve colour and vitality. Most successful keepers focus on water changes and stability rather than heavy dosing programmes.
Q: Are all Zoanthids safe to handle? A: Treat all Zoas as potentially toxic due to palytoxin—it's impossible to determine which species contain it without testing. Always wear nitrile gloves, eye protection, and ensure good ventilation. The risk is real but manageable with proper precautions.
Q: Why are my Zoas losing colour? A: Often due to lighting issues (too intense or insufficient), unstable nutrients, lack of feeding, or allelopathic effects from neighbouring corals. Gradually adjust light intensity, maintain consistent water chemistry, and implement regular feeding. Some fading is normal as colonies mature.
Q: Can Zoanthids thrive in nano tanks? A: Yes, they're excellent for nano reefs due to their moderate lighting requirements and parameter tolerance. However, they may spread aggressively in small systems - regular fragging helps keep colonies manageable. Consider compact-growing varieties for very small tanks.
