Hermit and blue leg crab death

[BlackFish]

So I'm two weeks out of my cycle in my BC29. I had two hermit crabs in for there two weeks cleaning the LR. They have been fine until yesterday one of them came out of his shell, so i went to the LFS and got a few larger shells, a blue leg hermit and a turbo snail. When i returned home the naked hermit was acting drunk (he couldn't stay upright). I sent a new shell next to him, he attempted to get in it but never did and soon died.I drip acclimated the new blue leg and turbo snail them added them, this morning the blue leg is out of his shell dead and the turbo never moved and the other original hermit is missing from his shell. The only other live stock is a single head zoa frag and a very small xenia frag, and both are doing fine.
Ammonia 0
Nitrite 0
Nitrite 5
PH 8.2
Alkalinity dkh 6 Meq/L 2.1
Salinity 1.022

 

[Tahoe61]

The victim hermit was probably in the process of molting. Hermits are viscous predators, they will kill and eat anything they can capture.
Eventually you will have to address the alkalinity level. Since you're keeping corals I would also bring the SG up to at least 1.024, closer to the value for NSW.

 

[BlackFish]

But all three hermits and the turbo snail died? The turbo never even moved after putting it into the tank. I am working on getting the SG up. What would you recommend for the alkalinity level? I only plan on keeping softies and some lps.

 

[Naiad]

Curious what is your mag? Do you currently have any living inverts or coral?

 

[BlackFish]

I don't have a Mag test yet. I have a single head zoa frag and a small frag of xenia.

 

[Naiad]

I don't have a Mag test yet. I have a single head zoa frag and a small frag of xenia.

If they are alive it rules out heavy metal contamination. High mag can cause inverts to wig out. Have you dosed anything or done wc recently that could change something?

 

[BlackFish]

I did a 5 gallon WC 6 days ago. No dosing yet

 

[BlackFish]

I was hoping to add fish soon, but now I'm not sure about it.

 

[Tahoe61]

Mag would have to be over 1600 to really start to see some possible adverse affects.
Unless you're dosing I highly doubt that is the case.
You probably had another un witnessed ammonia spike or nitrites, coupled with the lower SG that contributed to the demise of your inverts.
Alkalinity should be right around 7-9. Review the link below and aim for the values of normal salt water (NSW), the link will serve you well.

http://reefkeeping.com/issues/2004-05/rhf/