Banded urchin
Echinothrix calamaris
Also known as Banded longspine urchin, Double spined urchin, Banded sea urchin, Hatpin urchin
SaltwaterInvertebrate
Care at a glance
- Temperature
- 72–79°F
- 22–26°C
- pH
- 8.1–8.4
- Adult size
- 3.1 in
- 8 cm
- Minimum tank
- 50 gal
- 190 L
- Temperament
- Peaceful
- Social behavior
- Solitary
- Tankmates
- With caution
- Swim level
- Bottom
- Difficulty
- Medium
- Breeding
- No record
- Rarity
- Common
- Reef safe
- Reef safe with caution
- Family
- Diadematidae
- Origin
- Indo-Pacific lagoons and reef slopes, East Africa to Hawaii and French Polynesia
Overview
The banded urchin is a peaceful, nocturnal urchin and a very good algae grazer for a mature tank. It is best with a little experience.
Did you know
The banded urchin's two spine types have different jobs. The long banded spines are blunt and work as levers and armor, while the short dark ones are the weapons. Divers who brush against one get stung by spines they never saw.
Caring for the banded urchin
Keep the banded urchin in a mature tank of at least 50 gal (190 L), with film algae on the rock. Build solid, well-locked rockwork with cave gaps big enough for a spine span of 30 cm.
Hold the water at 72 to 79°F (22 to 26°C) with a pH of 8.1 to 8.4, and keep nitrate low. Drip acclimate it slowly. Spine loss means the water is wrong, and copper, high nitrate and salinity swings all cause it.
It grazes hair algae and coralline alike. Feed it dried seaweed once the algae is gone.
When the rock runs clean, it may nip at coral tissue and clams, so treat it as a reef caution. Its size and stiff spines also knock unglued frags off the rock. Keep it away from triggers, puffers and large wrasses, and handle it with tongs or a cup.
Good to know
Echinothrix calamaris is a diadematid urchin with two kinds of spines. The thick, hollow primary spines reach 10 to 15 cm and are usually banded light and dark. Between them sit shorter, needle-fine secondary spines that carry the venom. The test often shows a blue or green iridescent pattern between the spine bands. Juvenile cardinalfish shelter among the spines, and in Hawaii it hosts the small crab Echinoecus pentagonus. A sting feels like a bee sting and is not dangerous, but the thin spines break off in skin.
In the wild
The banded urchin lives in lagoons, channels and on outer reef slopes throughout the tropical Indo-Pacific. It ranges from East Africa and the Red Sea to Hawaii and French Polynesia, from the surface to about 70 m. It wedges into crevices and under ledges by day and comes out to graze at night.
Common questions
What size tank does a banded urchin need?
A banded urchin needs at least 50 gal (190 L). It spends most of its time in the bottom.
What temperature and pH does a banded urchin need?
A banded urchin is comfortable at 72–79°F (22–26°C) with a pH of 8.1–8.4.
What does a banded urchin eat?
A banded urchin grazes hair algae and coralline alike, and you can feed it dried seaweed once the algae is gone. When the rock runs clean, it may also nip at coral tissue and clams.
How big does a banded urchin get?
An adult banded urchin reaches about 3.1 in (8 cm).
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