TankBud

Mertens' carpet anemone

Stichodactyla mertensii

Also known as Mertensii Carpet Anemone, Giant Carpet Anemone

SaltwaterAnemone

Mertens' carpet anemone (Stichodactyla mertensii)
Brocken Inaglory · CC BY-SA 3.0

Care at a glance

Temperature
75–81°F
24–27°C
pH
8.1–8.4
Adult size
35.4 in
90 cm
Minimum tank
53 gal
200 L
Temperament
Aggressive
Social behavior
Solitary
Tankmates
With caution
Swim level
Bottom
Diet
Photosynthetic
Difficulty
Difficult
Breeding
No record
Rarity
Rare
Reef safe
Reef safe with caution
Family
Stichodactylidae
Origin
Indo-Pacific reefs (Red Sea to French Polynesia)

Overview

Mertens' carpet anemone is a huge, aggressive carpet anemone for a large reef display. It is a difficult animal for experienced keepers.

Did you know

A fully grown Mertens' carpet anemone can spread wider than a trash can lid. It is the largest sea anemone species known, edging out even the magnificent anemone for sheer surface area.

Caring for the Mertens' carpet anemone

Give Mertens' carpet anemone strong, stable lighting and vigorous flow across its whole surface. It needs a large footprint of rock or reef base to settle onto. A mature specimen can cover close to a meter of reef, so leave it years of room to grow into.

Keep the water at 75 to 81°F (24 to 27°C) with a pH of 8.1 to 8.4. Because of its eventual size, it is a long-term commitment best suited to a large, mature display of at least 53 gal (200 L). Acclimate it slowly and give it a stable home from the start. Repositioning a settled adult is difficult and stressful for the animal.

It draws most of its energy from symbiotic zooxanthellae. Once it is established, feed it large meaty items such as squid, shrimp or silversides every week.

It carries a powerful sting and, unusually for a carpet anemone, is aggressive toward tank mates. Give it at least a foot of clearance from any other coral or anemone. Never let it settle near a powerhead intake it could get drawn into.

Clark's and ocellaris clownfish are among the species most often seen hosting in it. It reproduces both sexually and by fission.

Good to know

Stichodactyla mertensii hosts more anemonefish species than any other single carpet anemone. Several of the Amphiprion species it hosts are not recorded on any other host.

In the wild

Mertens' carpet anemone ranges widely across the Indo-Pacific, from the Red Sea to French Polynesia. It attaches to hard reef substrate rather than burying in sand the way Haddon's and Gigantea carpets do.

Symbiotic relationships

Clownfish and their host anemones

A clownfish lives inside an anemone that stings and eats other fish its size. Its mucus coat keeps the anemone's stinging cells from firing, and a new fish builds that protection up over hours of brief touches. The fish gets a refuge no predator will follow it into and a nest site at the anemone's base. The anemone gets a guard that drives off the butterflyfish that would graze its tentacles, a steady supply of nitrogen from the fish's waste, and water movement at night, when the fish fans its fins among the tentacles and the anemone takes up more oxygen. Only ten anemone species host clownfish in the wild, and each clownfish species uses its own short list of them.

Captive-bred clownfish have never seen an anemone and do not need one; they settle for a coral, a powerhead or a corner of the tank. If you want the pairing, the anemone is the harder animal by far and goes in first, into a mature tank with strong light and stable water, at the tank size its own profile lists. The bubble tip anemone is the hardy host, and the one most clownfish accept in captivity even when it is not a natural host, so a clownfish profile lists it as the usual tank host where that is the case. The sebae, magnificent and carpet anemones are marked difficult, and the carpets eat fish. Expect a paired clownfish to defend its anemone against everything else in the tank.

Shrimp and crabs that live in anemones

Several small crustaceans live where almost nothing else can: among the tentacles of an anemone. Sexy shrimp perch in the tentacles in a cluster, bobbing their tails in the display that named them. The white-spot anemone shrimp is near transparent apart from its spots and lives on carpet anemones. The porcelain anemone crab sits at the anemone's edge and filters plankton from the water with two fan-like arms. Pederson's cleaner shrimp lives in the Caribbean corkscrew anemone and cleans fish from there. In every case the anemone is a bodyguard: its sting keeps off the small fish that would eat the shrimp. The anemone gains little, and the white-spot shrimp will nibble its host's tentacles when it is hungry.

Give each of them its anemone. Sexy shrimp take a rock flower anemone, a bubble tip or a carpet. The white-spot shrimp and the porcelain crab want a carpet anemone or a long tentacle anemone, both of which need a mature tank at the tank size their profiles list. Pederson's shrimp wants a corkscrew anemone or a condy. Without a host they perch on a coral or hide in the rock and are picked off by any fish that eats shrimp, so they suit a peaceful nano reef. A clownfish will evict them from an anemone it has claimed.

Every symbiotic relationship in the catalog

Common questions

What size tank does a Mertens' carpet anemone need?

A Mertens' carpet anemone needs at least 53 gal (200 L).

What temperature and pH does a Mertens' carpet anemone need?

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

What does a Mertens' carpet anemone eat?

A Mertens' carpet anemone draws most of its energy from symbiotic zooxanthellae. Once established, it takes a weekly feeding of large meaty items such as squid, shrimp or silversides.

How big does a Mertens' carpet anemone get?

An adult Mertens' carpet anemone reaches about 35.4 in (90 cm).

How does a Mertens' carpet anemone breed?

A Mertens' carpet anemone reproduces sexually and also by fission, splitting in two.

Related species