Christmas Tree Worm

Spirobranchus giganteus

Identification	Bright double-spiral crown in blue, orange, yellow, red, white, or multi-color — two spirals side by side. Permanently embedded in living stony coral, usually Porites or brain corals.
Maximum Length	1.5 inches (crown diameter)
Origin	Indo-Pacific, Caribbean, Red Sea
Minimum Tank Size	30 gallons
Reef Compatibility	Excellent — requires a healthy host coral

Behavior

Unlike most feather dusters, Christmas Tree Worms bore into and live permanently within living stony coral skeletons. Almost always sold attached to a coral fragment. Retracts into its coral instantly at any disturbance. Will not survive without the host coral remaining alive and healthy.

Diet & Feeding

Filter feeder. Captures phytoplankton and fine organic particles directly from the water column.

Cautions

The host coral must stay alive — this is the single most critical care requirement. The coral fragment (usually Porites) requires stable calcium (380–450 ppm), alkalinity (8–12 dKH), and pH (8.1–8.3). Do not allow the coral to bleach or die.