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
Swim level: Bottom
Difficulty: Difficult
Breeding: No record
Rarity: Rare
Reef safe: Reef safe with caution
Origin: Indo-Pacific reefs (Red Sea to French Polynesia)
Family: Stichodactylidae

Overview

Needs strong, stable lighting and vigorous flow across its whole surface, plus weekly feedings of large meaty items like squid, shrimp, or silverside once it is established. It carries a powerful sting and, unusually for a carpet anemone, is genuinely aggressive toward tankmates: give it at least a foot of clearance from any other coral or anemone, and never let it settle near a powerhead intake it could get drawn into. Clark's clownfish and ocellaris are among the most commonly seen hosts, and in the wild it accepts a broader range of anemonefish species than any of its relatives. Because of its eventual size this is a long term commitment best suited to a large, mature display; acclimate it slowly and give it a stable home from the start, since repositioning a settled adult is difficult and stressful for the animal.

In the wild

Ranges widely across the Indo-Pacific from the Red Sea to French Polynesia, where it attaches to hard reef substrate rather than burying in sand the way Haddon's and gigantea carpets do. It is the largest sea anemone in the hobby by surface area, with a mature specimen capable of covering close to a meter of reef, so it needs a large footprint of rock or reef base to settle onto and years of room to grow into. It hosts a broader range of clownfish species than any other carpet anemone.

Good to know

Stichodactyla mertensii holds the record as the largest known sea anemone species, with an oral disc that can exceed a meter across, larger even than Heteractis magnifica. It draws most of its energy from symbiotic zooxanthellae, reproduces both sexually and by fission, and hosts more anemonefish species than any other single carpet anemone, including several Amphiprion species not recorded on any other host.

Did you know

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