Black Longspine Urchin (Diadema sp.)

The Black Longspine Urchin (Diadema sp.) brings a striking silhouette and steady grazing activity to an established saltwater aquarium. Its slender black spines extend well beyond its small body, so open space matters as much as water volume. Sold individually, one urchin per order quantity.

Care at a glance

• Environment: Established saltwater aquarium with mature live rock and room to graze.
• Diet: Algae grazer; supplement with plain dried marine seaweed as needed.
• Temperament: Peaceful, with very sharp defensive spines.
• Reef compatibility: Generally compatible, but grazing and movement can disturb loose frags and coralline algae.
• Water: Stable marine conditions; avoid sudden changes in temperature or salinity.
• Identification: Diadema sp. Representative image shows Diadema setosum; species and appearance can vary by shipment.

A home with space to roam

Arrange secure rockwork with sheltered resting places and broad routes between rocks. Allow clearance for the full spine span when planning the aquascape. A small purchase size does not mean a small adult footprint. Keep coral frags firmly mounted and leave delicate specimens out of narrow travel paths.

Longspine urchins often shelter during bright periods and become more active as the lights dim. Observe its grip and grazing regularly. Acclimate carefully to the aquarium's salinity and temperature, and avoid copper medications in its system.

Feeding and compatibility

Natural algae should provide ongoing grazing opportunities. Once the rocks look clean, offer small portions of BRS Nori Seaweed Sheets within reach and remove uneaten pieces. Watch whether the urchin actually eats; a clean aquarium may not provide enough food for a large grazer.

Choose tankmates that will leave the urchin alone. Do not assume its spines make it safe with animals known to eat or pick at invertebrates. Plan maintenance around its location, and never grasp it with bare hands. Its fragile spines can puncture skin and break.

Explore other grazers

Compare the more compact Blue Tuxedo Urchin and Pincushion Urchin, or browse our Invertebrates. Choose a cleanup crew to fit the available food and space.

Frequently asked questions

How many do I receive?
One urchin. Each quantity selected represents one animal.

Will it live on algae alone?
Only when the aquarium supplies enough suitable algae. Check feeding and supplement with marine seaweed when grazing becomes scarce.

Can I pick it up by its spines?
No. Ask us about safe transfer and placement at pickup, and avoid handling the spines.

Is every black longspine the same species?
No. Several Diadema species share this common name. Ask us to confirm the current animal's identity and size before choosing it for your aquarium.