Palythoa Grandis

Palythoa grandis lives in the western Atlantic and is one of the largest-polyp species in its genus, with an oral disc that can exceed 2.5 cm. Its polyps stand on short, thick stalks and, although close together, do not form a dense carpet. The oral disc is broad and flat with thin tentacles around the edge; its color is in shades of brown, golden yellow, orangey or green. It was formerly also known as Protopalythoa grandis.

In the trade the name "grandis" is used loosely for many large-polyp Palythoa; some of the "grandis" on sale are actually other species from the Indo-Pacific. Their care is largely the same.

Palytoxin warning: The palytoxin level of this species is not known for certain; like other Palythoa, it should be considered toxic. Use gloves and protective eyewear, do not touch it with cuts on your hands, do not put rock with colonies in boiling water and do not scrub it out of the water. At any sign of poisoning, see a doctor immediately (in Türkiye, the National Poison Information Center: 114).

It lives in the Caribbean and Florida, usually at depths of 12–40 meters, on sheltered rock faces and rocky bottoms. It is not common in the wild; it is found singly or in small groups.

• Light: Moderate light (about 80–150 PAR); it can be acclimated slowly to stronger light. Because it comes from relatively deep water, it may bleach under sudden strong light.
• Flow: Moderate and random; detritus should not build up on the broad discs, but the polyps should not be constantly battered.
• Placement: On its own rock in the middle or lower zone of the rockwork.
• Water parameters: Salinity 1.024–1.026; KH 7–11 dKH, calcium 400–450 mg/L, magnesium 1250–1350 mg/L. It likes water with some nutrients.

It is photosynthetic, but its large polyps also catch small meaty morsels. Feeding mysis, chopped krill or fine zooplankton 1–2 times a week increases polyp size and propagation.

It is not aggressive and does not sting its neighbors; however, its polyps multiply sideways, if slowly. Leave 5–8 cm of clear space from other corals. Stinging LPS corals and anemones burn the polyps. Some dwarf angelfish, butterflyfish and zoanthid-eating nudibranchs eat the polyps.

Individual polyps are cut from the base with a scalpel and glued to frag plugs. Do the cutting under water, with gloves and eye protection. Large polyps may stay closed for a few days after cutting; let the new pieces rest in low light.

• Polyps not opening: Too much light, strong direct flow and pests are the most common causes.
• Bleaching: If the light was increased suddenly, turn it back down and keep the polyps under moderate light for a few weeks.
• Melting: Remove polyps that melt after cutting immediately.