Pincushion Urchin (Lytechinus variegatus)

The Pincushion Urchin (Lytechinus variegatus) is the hardiest urchin in the hobby and the one worth starting with. It is a relentless grazer that works turf and hair algae off live rock all day, and unlike the big spiny urchins it is compact, short-spined, and far less likely to bulldoze your aquascape on the way past. It also has one genuinely endearing habit: it picks up shell fragments, bits of rubble, and stray snail shells and carries them around on its back as camouflage, so most of the time you are watching a slowly moving pile of debris rather than an urchin. Browse the rest of our saltwater livestock and supplies.

For a tank fighting hair algae, it is one of the most effective animals you can add. It will not solve the nutrient problem that caused the algae, but it will strip the rock clean while you fix the cause.

Care Guide

• Tank size: 20 to 30 gallons and up. What matters is live rock surface to graze, not water volume.
• Established tank required: it eats algae and biofilm off mature rock. A newly cycled tank cannot feed one, and a starving urchin is the main way people lose them.
• Diet: turf algae, hair algae, film algae, and leftover food. In a tank that is genuinely clean, supplement with dried nori on a clip or a sinking algae wafer a couple of times a week.
• Glue your frags down. It is less destructive than most urchins, but it will still nudge loose frags and pick up anything small enough to wear. Anything not attached is fair game.
• Water: 72 to 78°F, salinity 1.023 to 1.025, pH 8.1 to 8.4. Drip acclimate slowly over an hour or more. Echinoderms are far less tolerant of salinity swings than fish.
• Zero copper: copper-based medications are lethal to urchins. Never dose them in a tank holding one.
• Nitrate matters: they do poorly in high-nitrate systems. Keep up with water changes.
• It eats coralline too. Worth knowing if you have spent years growing purple coralline on the back wall. It does not discriminate between algae you want and algae you do not.

Specifications

Compatibility

Safe with corals, peaceful reef fish, and the rest of a cleanup crew. It handles a different job from the others, so it pairs naturally with Zebra Turbo Snails on film algae, Nassarius Snails in the sand bed, a Pitho Crab on bubble algae, and Peppermint Shrimp on Aiptasia.

Avoid keeping it with anything that eats echinoderms: triggers, large wrasses, puffers, and some angels will pick at an urchin until it fails. And remember it is an obstacle as much as a resident, so make sure the aquascape is stable enough that a wandering urchin cannot topple a rock.

Recommended Foods & Supplies

• Dried nori sheets on a feeding clip for when the algae runs out
• Zebra Turbo Snail and Nassarius Snail to round out the cleanup crew
• Pitho Crab if bubble algae is also part of the problem
• Browse the full saltwater selection

FAQ

Will it eat my hair algae?
Yes, and it is one of the better animals for the job. Give it a week or two on an established rock scape and the difference is obvious.

Why is it covered in shells and rubble?
That is normal and healthy. Pincushions collect debris and hold it against their body as camouflage. If yours is wearing half your sand bed, it is a happy urchin.

Will it knock over my corals?
It is gentler than most urchins, but it still wanders. Glue frags to the rock and it will move past them without incident. Anything loose can end up relocated or worn as a hat.

Is it safe to handle?
The spines are short and blunt compared to a long-spined urchin, and it is not venomous, but do not grab it. Move it with a container rather than your hand, both for your sake and its tube feet.

Mine is losing spines. What is wrong?
Usually acclimation shock, poor water quality, or copper exposure. Check salinity stability and nitrate first. Some spine loss right after introduction is common and recovers if conditions are good.

Will it eat my coralline algae?
Yes. It grazes coralline along with everything else. If you prize your purple back wall, this may not be the animal for that tank.