Where did my crabs go

[big fish]

I had about 7 small crabs in my 10gal. tank that I have had for about 2 weeks.
Today I have noticed that I can only fing 2 of them but there are shells laying on the bottom of the tank where did hey go. :notsure:
I put some larger shells in for them but they dont seem to be in thoes does anybody know what is going on please help

 

[fallinmor]

it's possible they molted and when a hermit molts it leaves the shel and comes bck to it later. more likely the other 2 killed the rest wait about a day or 2 if u still only see 2 then get more.