Everyday is never the same with saltwater

[mws]

Well, First is the mystery of the empty shells. I had put a handful of shells(toenail size) for the crabs yesterday, only one manage to change the house. Two hours later all the shells was gone.
All other crabs with the exception of the one wearing an old houses.
So the only suspicion I have is the tiger shrimp took it as a building material. Could it be possible?

Next I have two nems split yesterday
_one of my big GBTA's
_ another rock flower nem
I think it has something to do with moon/sun cycles, as I been reading a few reports of nems splitting.

And last but not least is my hippo tang got stung by the bristle worm. It has 5-6 bristles on it side. What the outcome of that would be?