Could My Crabs Have Died Molting from Anaerobic Bacteria?

[DinkDonk]

Hi everyone, it has been a long time since I have been to the hermitcrabassociation forums! School has been very busy for me this last year or so. Nonetheless, I do have a inquiry, might is be possible that my crabs are deceased?
 
I've had my 3, *medium-ish* crabs for nearly a year now, and I've seen my crabs molt successfully before, although I have noticed that for a very long time now, I haven't seen any of my other crabs resurface. I currently only have one crab up, but I haven't seen the other two for nearly three to four months. I  know that hermit crabs can take a long time to molt, some even taking a year or so, but I do have a worry that has recently come to mind. 

When I was setting up my crabitat nearly a year ago, I made a saltwater solution to prevent mold and bacteria, although I think I have added a little bit too much and Over-saturated the substrate mixture and possibly might have harbored anaerobic bacteria. 

I've heard that can kill crabs in large concentrations when they are molting. I am unsure about what to do, and I know it is very risky and very often not recommended to dig up the substrate, but I feel sad for my Orpheus that he had been alone for quite some time and unfortunately I have not been able to find any housemates for him yet. I do feel worried and I thought perhaps talking it out and being reasonable with it would be acceptable. Thank you all in advance.

P.S. I do see that it is nearly a year ever since I joined HCA! Happy early HCA cake day!

[Pumpkincrab]

Sadly I don't know much about bacteria, but there are other members on this forum who can help!
I can't help but notice we both live in Seattle! What a coincidence!

[curlysister]

What makes you think there could be a bacterial bloom? Is there a strange smell? Can you see discolored substrate along the sides of the glass?

[aussieJJDude]

Agree with Curly, anaerobic bacteria usually releases high amounts of H2S, so you'll normally smell a rotten egg smell or sulphur smell if its an anaerobic bacterial bloom.

(Usually the sand will discolour as well, like Curly said)

[wodesorel]

Having lived through a few bacterial blooms, you don't normally smell anything wrong until you start digging though. The discoloration can be limited to a central mass away from the glass as well.