TankBud

Christmas tree worm

Spirobranchus giganteus

Also known as Christmas Tree Worm Rock, Christmas Tree Tube Worm, Tree Worm

SaltwaterInvertebrate

Christmas tree worm (Spirobranchus giganteus)
Nhobgood Nick Hobgood · CC BY-SA 3.0

Care at a glance

Temperature
75–81°F
24–27°C
pH
8.1–8.4
Adult size
1.6 in
4 cm
Minimum tank
20 gal
75 L
Temperament
Peaceful
Social behavior
Social
Swim level
Bottom
Diet
Filter feeder
Difficulty
Difficult
Breeding
No record
Rarity
Common
Reef safe
Reef safe
Family
Serpulidae
Origin
Circumtropical reefs, embedded in living Porites and other stony coral heads.

Overview

The Christmas tree worm is a small filter-feeding worm for established reef tanks only. It suits experienced reef keepers.

Did you know

A Christmas tree worm and its host coral live together for years. The coral slowly grows up around the worm's tube.

Caring for the Christmas tree worm

Christmas tree worms are almost always sold on a piece of Porites coral studded with many worms. The real challenge is keeping that host coral alive, since the worms usually follow if it dies. Give the Porites strong light and strong flow in a mature tank of at least 20 gal (75 L).

Keep the water at 75 to 81°F (24 to 27°C) and a pH of 8.1 to 8.4. The worms are filter feeders, so feed them fine plankton regularly.

They are peaceful, reef safe and harmless to their tank mates. There is no record of them breeding in aquariums.

Good to know

Spirobranchus giganteus is a tube worm in the family Serpulidae. It builds a hard calcium tube inside a living coral, most often Porites. Its spiral crown works as both its gill and its feeding fan, straining plankton from the water. The crowns come in red, orange, blue, white and yellow.

In the wild

Christmas tree worms live on reefs around the tropics, set into Porites and other stony coral heads. Each worm shows two bright spiral crowns that stick up out of the coral like little fir trees. The crowns pull instantly into the hidden tube when a shadow passes.

Symbiotic relationships

Christmas tree worms and Porites

A Christmas tree worm settles as a larva on living Porites, and the coral grows up around its tube, so the adult worm lives embedded in a coral head with only its two spiral crowns showing. The crowns are gills and feeding nets; the worm snaps them back into the tube at a shadow and unfurls them again a minute later. The coral seems to gain from the tenant: a Porites head with worms in it suffers less from crown-of-thorns starfish, which avoid the worms' spiny tube plugs, and patches of coral around each worm have been seen to survive bleaching that killed the rest of the colony.

The worms are sold on a piece of living Porites, often called a worm rock, and they live only as long as the coral does. Treat it as a coral first: reef lighting, stable water, moderate flow. Feed the worms phytoplankton or a fine coral food a few times a week, since a home tank carries little natural plankton. A worm that loses its crown can regrow it, but a worm whose coral dies rarely lasts long, so keeping the Porites alive is the whole job.

Every symbiotic relationship in the catalog

Common questions

What size tank does a Christmas tree worm need?

A Christmas tree worm needs at least 20 gal (75 L). It spends most of its time in the bottom.

What temperature and pH does a Christmas tree worm need?

A Christmas tree worm is comfortable at 75–81°F (24–27°C) with a pH of 8.1–8.4.

What does a Christmas tree worm eat?

A Christmas tree worm is a filter feeder that needs regular feedings of fine plankton.

How big does a Christmas tree worm get?

An adult Christmas tree worm reaches about 1.6 in (4 cm).

Related species