TankBud

Porites

Also known as Christmas Tree Worm Rock, Worm Rock

SaltwaterCoral

Porites (Porites)
Louis Wray · CC BY-SA 3.0

Care at a glance

Temperature
75–81°F
24–27°C
pH
8.1–8.4
Adult size
13.8 in
35 cm
Minimum tank
40 gal
150 L
Temperament
Peaceful
Social behavior
Solitary
Swim level
Bottom
Difficulty
Medium
Breeding
Easy
Rarity
Common
Reef safe
Reef safe
Family
Poritidae
Origin
Widespread across Indo-Pacific reef flats and slopes

Overview

Porites is a widely aquacultured SPS coral, and it is fairly undemanding for one once established. It suits a keeper with a little experience.

Did you know

The colorful Christmas tree worms on Porites worm rock are not part of the coral at all. They are tube worms that bore into a living colony and live inside it for years. An old wild head can host dozens of their spiral crowns, and each worm snaps instantly into its tube at the slightest disturbance.

Caring for the Porites

Give Porites high light, in the range of 200 to 250 PAR or more, and moderate to strong flow. Do not aim the flow straight at the colony, since that can strip its short polyps and stop it from feeding. Set it in an open, high spot on the rockwork, like the reef flats it grows on.

It needs a tank of at least 40 gal (150 L). Keep the water at 75 to 81°F (24 to 27°C) and a pH of 8.1 to 8.4. Like any stony coral, it needs stable calcium, alkalinity and magnesium. Wild-collected colonies can be slow to settle in.

Porites is peaceful, and its short tentacles pose little threat to neighbors. Ordinary SPS spacing for growth is enough.

A piece kept to host Christmas tree worms is a different project. The worms need much more frequent feeding with fine planktonic foods than the coral does. That pulls the tank's nutrient levels in the opposite direction from what the Porites wants.

Good to know

Porites, family Poritidae, includes both branching and massive species. Branching species such as Porites cylindrica form low thickets and fields of gray or yellow fingers. Massive species such as Porites lutea build the large dome and boulder colonies that can dominate a reef flat and stand for centuries. The skeleton is made of very fine, densely packed corallites. That is part of why Christmas tree worms and other boring organisms can tunnel into a colony without killing it outright. Porites hosts zooxanthellae like other reef-building stony corals, and it grows its skeleton fastest under strong, direct light.

In the wild

Porites is a widespread Indo-Pacific genus that builds some of the largest and oldest colonies on the reef. It grows in full sun on shallow reef flats and slopes.

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 Porites need?

A Porites needs at least 40 gal (150 L).

What temperature and pH does a Porites need?

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

How big does a Porites get?

An adult Porites reaches about 13.8 in (35 cm).

Related species