Palythoa grandis (Magnificent Sea Mat) Care Guide
Palythoa grandis is a large-polyped zoanthid with fleshy skirts that responds well to feeding. It contains palytoxin, so protective handling is essential.
Compiled by Aquairi from published sources · Published · Updated
Overview
Palythoa grandis is a large-polyped colonial zoanthid with prominent fleshy skirts. Its polyps are noticeably bigger than those of small zoanthids, with flattened oral discs ringed by tentacles. It is zooxanthellate but, given its large polyps, is also an active feeder.
Taxonomy
- Order: Zoantharia
- Family: Sphenopidae
- Genus: Palythoa
- Scientific name: Palythoa grandis (Verrill, 1900) (WoRMS AphiaID 288461; originally described as Protopalythoa grandis)
Habitat
The species is recorded from the Caribbean and Indo-Pacific, where its large polyps grow embedded in an encrusting coenenchyme on reef substrate.
Reef tank requirements
- Temperature: 24-26 °C (75-79 °F)
- Specific gravity: 1.024-1.026
- pH: 8.1-8.4
- Alkalinity (dKH): 8-11
- Calcium: 380-450 ppm
- Magnesium: 1280-1350 ppm
- Lighting: 75-200 PAR (medium)
- Flow: medium
- Recommended tank maturity: about 3 months
Care and feeding
Palythoa grandis is hardy and beginner-friendly when parameters are stable. Because of its large polyps it does best with regular spot-feeding of meaty foods such as mysis, alongside fine reef foods and amino acids, in addition to the energy it gets from photosynthesis. Provide medium lighting and moderate flow.
Compatibility
It is peaceful and reef-safe with fish and shrimp. As an encrusting colony it can spread, so leave room around it to avoid contact with other corals.
Palythoa grandis Propagation Guide
Overview
Palythoa grandis (family Sphenopidae) is a large-polyped Palythoa often called a sun polyp, with single polyps growing to over two inches across - among the largest photosynthetic zoanthids kept by aquarists. Its polyps sit on a colonial coenenchyme mat. Reef Builders describes it as comparatively slow-growing and as one of the slimiest and most toxic of all zoanthids.
Reproductive Mode
This species is increased asexually. New polyps bud from the colonial mat, but growth is comparatively slow, so colonies build up gradually from one or two polyps over long periods. Propagation divides the colonial clusters once enough polyps have accumulated.
Fragging / Asexual Propagation
Because polyps are large and the colony slow to rebuild, frag conservatively. Following Reef Builders' zoanthid method, slice the mat between polyps with a razor blade and trace the line with coral cutters until a polyp or cluster frees, cutting close to the base. Mount the cluster on a plug and allow a long recovery.
- Wear gloves, eye protection and a mask - this is one of the most toxic zoanthids.
- Cut the colonial mat between large polyps with a fresh razor blade.
- Trace the line with coral cutters until a polyp or cluster separates near the base.
- Dry the plug and base, add a little glue, and seat the cluster gently.
- Return it, blast off the copious mucus, and allow extended time to re-anchor and bud.
Conditions for Propagation
- Lighting: 75-200 PAR (medium)
- Flow: medium
- Temperature: 24-26 degC
- pH: 8.1-8.4; salinity 1.024-1.026
- Large polyps accept meaty foods, which can support recovery
Palytoxin Safety
Palytoxin is one of the most poisonous non-protein substances known, and aquarists have been poisoned by contact and by inhaling aerosol when handling or removing Palythoa. Given how much mucus this species produces, eye and face protection is essential during any propagation work.
Common Challenges
Slow growth means a fragged colony takes a long time to rebuild, so over-fragging sets the parent back severely. The heavy mucus can smother fresh frags if not blasted off, and large polyps are easily damaged by deep cuts. Frag minimally, cut cleanly, and be patient through recovery.