Blue Tuxedo Urchin (Mespilia globulus)

The Blue Tuxedo Urchin (Mespilia globulus) is a small, round sea urchin dressed in rows of short spines separated by broad, velvety bands of deep teal blue, the "tuxedo" that gives it its name. It spends its days grazing film algae and hair algae off rock and glass, often wearing a little hat of shell bits, rubble, or algae that it picks up and carries around. It stays small, it is peaceful with fish, and it is one of the most charming members of a reef cleanup crew. Browse the rest of our invertebrates and our saltwater livestock and supplies.

Care Guide

• Tank size: 20 gallons or larger, established, with plenty of live rock to graze.
• Diet: herbivore. It lives on film algae, hair algae, and biofilm. When the tank runs clean, it starves quietly, so offer dried seaweed on a clip a few times a week.
• Frags: glue or firmly seat every frag and loose rock. An unsecured frag plug is fair game to be carried off or tipped over.
• Water: 72 to 78°F, salinity 1.023 to 1.026, pH 8.1 to 8.4. Urchins are very sensitive to salinity swings, low oxygen, and any copper, so never dose copper-based medications in its tank.
• Acclimation: slow drip over 45 minutes or more. Invertebrates do not tolerate sudden salinity changes.
• Escape routes: it can climb into overflows and wedge into pump intakes, so cover them.
• How many: one per 20 to 30 gallons is plenty. More than that and they will run out of algae.

Specifications

Compatibility

Peaceful toward fish, shrimp, snails, clams, and corals. It works well alongside the rest of a cleanup crew such as Cerith Snails, and with other grazers like the Purple Pincushion Urchin in a larger tank with enough algae for both. Avoid triggerfish, puffers, large wrasses, and big hermit or arrow crabs, all of which will prey on urchins. In a reef, the only real conflicts are loose frags and coralline algae, so secure your corals and accept a few grazed patches on the rock.

Recommended Foods & Supplies

• BRS Nori Seaweed Sheets, a supplemental graze when algae runs low
• Two Little Fishies SeaVeggies Green Seaweed
• Two Little Fishies VeggieMag Seaweed Clip to hold seaweed low where it can reach
• Salifert Copper Test Kit to confirm a tank is copper free before adding inverts
• Saltwater Refractometer for stable salinity

FAQ

Why is it carrying shells and rubble around?
Tuxedo urchins hold debris on their spines and tube feet, likely as shade and camouflage. It is normal behavior and one of the most entertaining things about them.

Will it knock over my corals?
It can move or tip small frags that are not attached. Glue frags to rock or seat plugs firmly and it will simply graze around them.

Does it eat coralline algae?
Yes, along with the nuisance algae. Expect some pale grazed patches on the rock over time. Most reefers consider that a fair trade.

Are the spines dangerous?
No. The spines are short and not a meaningful hazard to people, though it is still best to handle it gently, underwater, and without squeezing.

What if my tank runs out of algae?
Feed dried seaweed on a clip a few times a week. A slowly shrinking, spine-dropping urchin is usually a hungry one.