Zoanthids and Palythoa (Zoanthus spp. / Palythoa spp.)

Taxonomy & Identity

Zoanthids (often called "zoas") and their relatives Palythoa ("palys") are colonial polyp animals that are among the most popular and collectible corals in the hobby. Their incredible color diversity, ease of care, and rapid reproduction have created an entire sub-hobby of zoanthid collecting, with rare morphs commanding premium prices.

Natural Habitat & Distribution

Zoanthids and Palythoa are found in tropical and subtropical waters worldwide, from the Caribbean to the Indo-Pacific. They inhabit various zones from intertidal areas to deeper reefs. Zoanthus species typically prefer slightly deeper, more stable environments while Palythoa often tolerate shallow, variable conditions.

Morphology & Growth Forms

Both groups form colonial mats of individual polyps connected by a common tissue (coenenchyme). Zoanthus polyps are smaller with delicate skirts and incredible color variety. Palythoa tend to be larger with more muted colors but greater hardiness. Protopalythoa fall somewhere between. Colors and patterns are virtually unlimited— solid, striped, spotted, and multicolored morphs exist.

Lighting Requirements & Spectrum

• Intensity: Low to high (adaptable)
• Target PAR: 50–300

Zoanthids are remarkably adaptable to lighting conditions. They can thrive under low light and gradually adapt to intense illumination. Colors may shift based on lighting—many develop better fluorescence under blue-heavy spectrums. Acclimate slowly to prevent bleaching when moving to brighter conditions.

Flow Requirements & Patterns

• Intensity: Low to moderate
• Type: Gentle, indirect

Moderate flow helps keep polyps clean and delivers food particles. Excessive flow can prevent polyps from opening fully. Zoanthids are quite tolerant but display best with gentle water movement. Ensure enough flow to prevent detritus accumulation on the colony.

Nutrient Dynamics & Water Chemistry

Zoanthids are incredibly tolerant of water parameter variations. They thrive in nutrient-rich systems where many other corals struggle. This hardiness makes them excellent beginner corals. However, basic stability is still beneficial for optimal growth and coloration.

Feeding Biology & Symbiosis

Zoanthids contain zooxanthellae and photosynthesize but are also capable predators. They readily capture and consume various food sources, which can accelerate growth.

• Mysis and brine shrimp
• Cyclopeeze and similar small foods
• Reef Roids and coral powders
• Dissolved organic matter

Regular feeding isn't essential but promotes faster colony growth. Broadcast feeding works well as polyps will catch passing particles.

Common Diseases, Pests & Predators

• Zoanthid-eating nudibranchs – color-matched, hard to spot
• Zoanthid-eating spiders (sea spiders)
• Sundial snails
• Zoa pox – appears as white spots on closed polyps

Quarantine and dipping new additions is important. Inspect carefully for nudibranchs which often match their host's colors perfectly. Zoa pox can be treated with various dips. Keep colonies healthy with good flow and clean water.

Compatibility & Placement

Zoanthids are semi-aggressive and will overgrow slower-growing corals if given the chance. They spread across rockwork rapidly. Most fish ignore them, though some species may pick at polyps. They can coexist with many coral types with proper spacing.

• Best zone: Any level depending on species
• Give space: Will spread; plan for growth
• Isolate: Consider dedicated zoa rocks to control spread

Fragging Techniques

Zoanthids frag easily—simply cut through the mat with a razor blade or scalpel, ensuring each piece has several polyps. Glue to frag plugs or rock. They can also be encouraged to spread onto adjacent plugs naturally. Handle with care due to palytoxin concerns (see warning below).

Aquacultured Strains & Trade Names

The zoanthid naming world is extensive: "Fruit Loops," "Utter Chaos," "Sunny D," "Eagle Eyes," "Purple People Eaters," "Fire and Ice," "Rastas," "Gobstoppers," and hundreds more. Rare morphs can sell for hundreds of dollars per polyp. Many are aquacultured and hardy.

Safety Warning: Palytoxin

IMPORTANT: Some Palythoa and related species contain palytoxin, one of the most toxic substances known. Never boil, microwave, or burn live rock with zoas. Wear gloves when handling, especially when fragging. Avoid getting slime in eyes, mouth, or open wounds. Seek medical attention if exposure occurs and symptoms develop. Most aquarium zoanthids pose minimal risk with normal handling but caution is warranted.

Difficulty Rating & Summary

Difficulty: Beginner

Zoanthids are among the easiest and most rewarding corals for beginners. Their hardiness, incredible color diversity, and collectibility have made them hobby favorites. The vast array of morphs means there's always something new to discover. Just handle with appropriate caution due to potential palytoxin content.