Something killing hermits...

First off, parameters are fine.
Something is killing my hermits, I have had 3 die already. I thought it was from the end of my cycle which could have killed the first 2, however I came home today to find another dead hermit body out of the shell laying around the sand and also a cave of sand which seems to be dugout. I moved my powerheads recently but I am almost positive this sand digging was not caused by waterflow. Here is a pic of what it looks like. Reefcleaners is having a sale and I really wanted to order some CuC's today, do you think it is a bad idea based off whats going on?

 

Since there's an area dug out, it could be a mantis....

 

They may be molts also.

 

I really don't know but i have heard this before, that sometimes when tanks arn't mature enough (not just cycled but set up for awhile) they can have problems and slowly die off.

thats sorta what happened with mine I'm guessing.

 

I notice my hermit crabs die off sometimes one or two at a time... I started with about 20-24 and have maybe 6-8 left. I've seen them fight each other, so maybe that's all it is.

Whatever you do tho, do NOT... I repeat...DO NOT call the police and report a serial killer is on the loose.

They told me that if I did it again they would charge me with filing a false report.

 

Probably not a mantis. If it was a mantis you wouldn't see the dead bodies you would see a shell broken to pieces. Also that looks to be a fairly large dug out area for a mantis. In my experience they only dig out barely more than they need.

 

If possible, check out their shells and try and remember which crab has which shell. Sometimes they will fight and kill each other to take over their shells when theirs is pretty much outgrown. Throwing a few empty shells will usually solve this problem.

- Mag.

 

I have tons of empty shells in there for them. Do hermits really molt?

 

yes, they do molt.

 

So is the best approach to figuring this out, when the tank lights go out just watch for a long time for anything moving in that cave?