A cold-water anemone of the North Pacific that does not belong in a tropical reef tank. An aquarium reference gives about 6-20 °C and a modelled estimate runs colder still, so it needs a chilled temperate system. It stings and eats fish and shrimp that come within reach, so keep small tankmates away from it. Read the name with care: this animal is often kept under the older name Urticina crassicornis, and a piece of unknown origin cannot be proven, so check your animal.
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Typically about 20 cm high with a column about 15 cm across, occasionally to 50 cm high.
Lifespan
—
Social needs
solo
Native region
North Pacific, including the American coast from Alaska to California (uncommon in California)
Origin
Worldwide
Climate
Temperate
Water type
Marine
Family
Tealidae
Genus
Urticina
Part of the Sea Anemones
Stinging, sessile cnidarians ranging from clownfish-hosting giants to nano-sized carpet species. Many are demanding, mobile, and can sting corals or be drawn into pumps — careful placement and rock-stable water are essential.
Not a tropical animal. Keep it only in a chilled temperate tank. One aquarium reference, written under the older name, gives about 6-20 °C (43-68 °F), while one modelled preference sits far lower, near 0-11 °C, so aim for the cool end. Wild animals sit on the low shore and in shallow subtidal water, often under boulders, to past 30 m.
It lives in the North Pacific. On the American coast, records run from the Pribilof Islands in Alaska to about Monterey, with rarer records further south, and it also occurs in the north-west Pacific around Kamchatka.
Substrate
Give it stable rock with overhangs or the underside of large stones, since wild animals often hang beneath boulders.
Equipment & setup
A chiller is essential, sized to hold the tank cold through warm weather. Add a thermometer you check daily, moderate flow and good oxygenation.
Diet
Must be fed. No source reports algae in its tissue, so do not count on light. Wild prey includes crabs, sea urchins, mussels, snails, chitons, barnacles and fish. Offer pieces of fish, shrimp or mussel. No source gives a captive feeding schedule.
Behavior & temperament
A solitary, slow-moving predator that takes prey with stinging tentacles. Its column is often blotched red and green, and the tentacles are usually banded. A lifespan of 60 to 80 years is reported for Pacific coast animals, with no study behind it in the sources checked, and it should not be read as an aquarium figure. The candy-striped shrimp Lebbeus grandimanus lives with it there. The name is tangled: the true U. crassicornis has a smooth column and broods its young, while this animal has a column covered in vesicles, and many pictures labelled with the old name show it.
Health
Not a tropical animal. A warm reef tank runs hotter than any temperature reported for it, so keep it out of normal reef systems. Warm water is the main threat, and a chiller failure is an emergency. It also stings and eats fish and shrimp that come within reach. Its effect on people is listed as unknown, so wear gloves.
Tips, DIY & hacks
This is not a reef animal. Do not add it to a tropical reef tank. Set up a chilled system and prove it holds temperature first. It stings and eats fish and shrimp that come within reach, so keep small tankmates away from it. Check what you actually have, because a trade piece of unknown origin cannot be proven: a column covered in vesicles means U. grebelnyi, while a smooth column means true U. crassicornis (Atlantic and Arctic) or, in the North Pacific, U. timuri. Do not expect small pieces to match the descriptions here.
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Temperate
Marine