Sea urchin feeding on sps

[nashorn]

I picked up a long spine urchin a few weeks ago since I read they were reef safe.
At first it seem safe just feeding on the on the live rocks. Then I notice it on one of my sps but thought it's just moving around.
Next day I found damage to that coral but maybe it's just a coincidence.
But then it happen again the urchin moved on to another sps and the
So I moved it to my QT and sure enough it started to feed on my frags.
I have other smaller urchins and will be keeping an eye on them from now on.

 

[Best Fish-Jake]

It doesn't happen too often, but once in a blue moon urchins will eat hard coral. A tank's coraline algae is usually enough to supply the urchin with its needed calcium so corals aren't generally at risk.

Do you have any pictures of the damage? It's more likely that the urchin's spines damaged the coral than the urchin was actually eating the coral.