Urchins for your Reef
Urchins are nocturnal, slow moving and 95% reef safe. Occasionally they will eat zooanthids and polyps.
Drip acclamation is absolutely necessary. Stick to smaller specimens. All love algae including hair algae They grind away rock and poop out sand the top. I watched a pencil urchin hide in a crevice during the day, roam the tank at night then return to the exact spot each morning.
Purple Pin Cushion
have hair thin feelers between their spines that pick up things and carry them around.
The spines are solid calcium carbonate aka chalk.
have feelers too but carry much less. The bare sections are blue and brown.
I’ve seen these with 30+ inch spines while snorkeling and they grow very fast. Small fish will live amongest the spines of larger urchins.
Red Slate Pencil
The Hawaiian species has very thick spines covered in deep red coralline algae.