My New Tank

[sash]

I just took over a tank from a friend.
65 gal. and 2 fish (yellow tang and a puffer,as well as a hermit crab).
I put on top of that a coral beauty, a tang(purple with a yellow rim around the eyes??)
a cleaner wrasse and a emerald crab.
When I put some liverock in the tank I found the emerald crab dead and I don't know when it happened because it was still alive 2 days ago.Who could have killed it or does it die just like that? On another topic are there any inverts or corals that I could put with that?
Thanks

 

[who dey]

are you testing your water parameters (i hope) if you just added some new LR you quite possibly may have had an ammonia spike

 

[sash]

just checked them and it said they are o.k.
But I don't know how old the tests are. what should I do?

 

[xjayx]

maybe the puffer?
They'd probably eat inverts...
and another thing...
Are you sure the crab is dead?
I'm new to this hoby and thought my poor crab died this morning.
I pulled it out and threw it away and everything...
Turns out what I saw and threw out wasn't the actual crab but her shell left behind after she molted.
She actually left her whole intact shell out.
It looked JUST like a dead crab to me.
But later... to my surprise, there she was... hiding in a corner still in my tank.