Generally speaking, yes, Longspine Urchins are reef
compatible. I wouldn't go as far as to say that they are reef
safe though, not meaning they will eat coral, but rather bulldoze their way through it. Polyps, Zoanthids, Monti's, Mushrooms, basically anything that is low enough for them to crawl onto is at risk of being knocked loose. They are slightly poisonous as well, so extra care should be taken when handling them or while doing tank maintenance. Although a sting won't kill you, it will leave your arm cramped and aching for hours (which can get fairly irritating.) It is mainly a nocturnal animal, so do not be discouraged if you don't see them out much during the lighted hours. They are also invert-safe, so don't be worried about your crabs, snails or shrimp being consumed.
Though do take heed, Longspine Urchins can be moderately difficult to maintain if there is an insufficient amount of algae provided for them. Sand shrimp, veggie flakes and dried seaweed can be supplemented on a weekly bases. And some of your Coraline
will be scraped off (hence the white trail.) They are
very sensitive to levels of Nitrate, and if it sheds its spines, that means your water parameters are inhabitable for them. If one does happen to kick the bucket, it should be removed immediately after death, they will sometimes void the venom from their spines which is very dangerous to the other livestock's safety.
Now that you know more about the Longspine, you can decide for yourself if you would find them appealing in your current setup. They are more commonly seen in Predator tanks and FOWLR's than Reef systems. But when the proper precautions are taken into consideration and the caretaker accepts the responsibility, they make quite an eye-poping addition to an already astounding reef.
