bloodthirsty pencil urchin

[jon123]

My pencil urchin ate 3 legs and 1/2 the disk off my chocolate chip starfish. As soon as i noticed i separated them, bu my brittle stars, cb shrimp, and fish ripped the shredded starfish apart and ate the remainder. Now, my question is, is this common? has anyone had this happen before? i talked to my lfs today and he said one other person had told him about this concerning a pencil urchin they purchased around the same time as me. I have a second chocolate chip starfish in the tank, should i be concerned? the 3 had been together for about 5 months. Perhaps the starfish was dying?
any help or thoughts appreciated!
Jon

 

[ophiura]

It is entirely possible it was dying. To start on that front...what did you feed the star? What are your water parameters, especially specific gravity?
IMO, true pencil urchins are NOT reef safe, IMO and do threaten things like soft corals and such. But in this case I am wondering if the star was dying and or dead and this caused everyone to eat it

 

[jon123]

the star wasnt dead, but it may have been dying. i know it wasnt dead because its tube feet were still moving enough for it to pull itself under a rock with 3 legs and 1/2 a disk.
the water quality is normal and my other star, fish, shrimp, snails, urchin, and brittles are all acting normal.
and i fed the star krill and silversides, mabe 1-3 times a week depending on when it came to the top and flopped over its arms.
Jon

 

[ophiura]

I am not sure how it started but don't rely on the animal coming to the top to indicate it is hungry. People have decided this is what it means but it can mean several more likely things. So I would feed them more consistently regardless of their behavior.
At least specific gravity should be 1.025-1.026.