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Yeah, looks like E. tribuloides to me. Not sure on the clam eating, but with regards to the coral eating:I’m assuming it’s a standard Slate pencil urchin
For the pencil urchin (the top one is scientific study based, the bottom one is aquarium hobby/industry observations):
Yeah, from what I can find, these guys are technically considered spongivores* (i.e. they prefer to eat sponges), but when they can't get sponges they've been found to eat just about literally anything (one study found that these would even eat the wooden or fiberglass tank walls if starved enough**); so I'd imagine that how reef-safe they are likely depends on how much food they have available that they would prefer over the corals in the tank.
*Source:
**Source:Spongivory by Eucidaris tribuloides from Salvador, Bahia (Echinodermata: Echinoidea) | Journal of the Marine Biological Association of the United Kingdom | Cambridge Core
Spongivory by Eucidaris tribuloides from Salvador, Bahia (Echinodermata: Echinoidea) - Volume 82 Issue 2www.cambridge.org
Looks to be Eucidaris tribuloides:
"its search for food, which can include sponges, corals, bivalves, gastropods, bryozoans, along with detritus and some algae."*
"It feeds primarily on algae and coral but they can feed on small invertebrates as well. "**
*Source:
**Source:Section: Urchins: Group: Common Urchins: Species: Eucidaris tribuloides (Mine Urchin, Slate Urchin, Club Urchin, Pencil Urchin)
Marine Aquarium Library: Common Urchins, Order: Cidaroida - Family Cidaridae, Eucidaris tribuloideswww.saltcorner.com
Pencil Urchin -
E-1621 PENCIL URCHIN, Eucidaris tribuloides This sluggish, nocturnal sea urchin has thick, wooden like spines. It feeds primarily on algae and coral but they can feed on small invertebrates as well. They are a very hardy species and can range from a light brown to a reddish brown. HABITAT They...gulfspecimen.org
Edit: From the threads I've seen about damage caused by these guys, it seems they prefer to eat LPS.
Yeah, looks like E. tribuloides to me. Not sure on the clam eating, but with regards to the coral eating: