Good question, I suppose I need some credentials.
Well, I'm a biologist, and Sponsorship Secretary of the Las Vegas Valley Reefers club here in LV, reefkeeper & diver. I went diving on a remote fringing reef in Tobago north of Charlotteville, saw about est. 5000 of them living on the rocks of a small area around Elkhorn Coral, zooanthids, and brain corals. some of the rocks were covered with urchins completely. They had trimmed the hair algae on the rock right up to the edge of the corals. Leaving the corals unharmed. One has to wonder, with such extreme density, why an urchin would not even accidentally eat the coral.
I went home, bought 3 from Pacific East Aquaculture, and got a 4th one later from Atlantis, and they have been living in my 180 gallon reef for about 3 years now. They are still small, and they don't eat coral. There are also other people who say the same thing.
So now I recommend them to people, based on my experience over the past few years. Plus, I like to give an alternative to the long-spine diadema urchins, that grow to be the size of basketballs, have you actually seen how big these get? They're even venomous. Who exactly is keeping this urchin long term? If at all? it's even in books written by experts on the subject that they are great for algae control. A 3ft. diameter ball of posionous sharp spines for algae control, that doesn't sound all that great to me.
