Rainbow Spectrum zoas

Rainbow Spectrum is a multicolor zoanthid strain whose polyps carry several colors at once — a green to yellow mouth, an orange to red ring, and a skirt that shifts between purple and teal depending on the light. No two polyps on a frag are patterned exactly alike, which is the appeal: a grown-out mat reads like a scatter of small rainbow discs rather than a single flat color.

Like most Zoanthus strains it is a forgiving coral. It opens under low to medium light (about 75 to 200 PAR) and moderate, indirect flow that keeps the mat clean without folding the polyps over. Color intensity tracks light more than food: spectrum polyps kept too low stretch and dull, while polyps given a little more blue light tighten up and show the full ring pattern.

Zoanthids feed mostly from their zooxanthellae, so light matters more than target feeding, but most colonies respond well to a light broadcast of fine planktonic food or amino supplements once a week. Keep nutrients present rather than zeroed out — colonies kept in ultra-low-nutrient water often stall, shrink, or close up. Stable alkalinity between 8 and 10 dKH, calcium 400 to 450 ppm, salinity around 1.025 to 1.026, and temperatures of 77 to 79°F cover the basics.

Placement is about growth control as much as light. Zoanthids spread by a creeping mat and will overgrow slower neighbors, so many keepers give a named strain its own rock island with sand on all sides. A new frag should start low while it acclimates, then move up gradually if you want tighter polyps and stronger color.

Handling note: zoanthids can contain palytoxin. Wear gloves and eye protection when handling or fragging, wash hands afterward, and never boil or pressure-wash zoanthid-covered rock.

Field notes — what keepers report

Keepers report the skirt color is the variable part — the same colony can read purple under whiter light and teal-green under heavy blue, so photos of this strain vary a lot between tanks. Several keepers say new growth at the mat edge shows the brightest rings, with older center polyps going slightly darker. Growth is reported as steady rather than explosive for a zoa, and colonies are said to sulk for a few days after fragging before reopening fully.