Dead fiddler crab

[fishb0ne]

I hope I'm posting in the right section.
It's not a disease, at least don't think so.

Tonight I had my second fiddler crab female fatality.
First one died about a month ago, but that was an understandable loss. She was very tiny and has gone through some rough times, lost a pincher and almost all legs on one side except for one, from a fight with a red claw.
This one thought, I just found upside down, dead for no apparent reason. She has been carrying eggs for a while.

Some facts about the medium I'm keeping them in. It's a 75g paludarium, half beach half brackish.
Water parameters:
temperature: steady 78*F
ambient temp: steady 74*F
ammonia: 0
nitrIte: 0
nitrate: 5
ph: 8.3
water gravity: 1.006

I did a liquid test just now.
All the other 8 crabs seem to be doing fine. They're munching on my floating plants [grr], eagerly accepted the peas I dropped just now, they're very lively.

Something else I'm missing, or should I just dismiss this as a "regular" death and move on?
I'd say she was fully grown and had her for about 3 months, bought from the LFS. Maybe it was old age?

[Zagz]

I missed this post sorry. Also sorry for your loss. I don't know much about fiddler crabs. If there were no physical signs of illness I would keep an eye on the rest of the crabs and their behaviours. You could always ask at the lfs and see if they know how the crab was when they got it.

[fishb0ne]

I would have tried that but I already know the condition, they basically got them 3 or 4 days before I purchased them. As it is typical with LFS, they kept them in freshwater ...
The other ones seem to be doing just fine, I even caught a couple mating

[roka64]

How long did you acclimate them?

[fishb0ne]

An hour, just like with all my crabs.
I'd think that if it was due to acclimation, it would have died sooner? It has already moulted once.

[roka64]

Hmmm, I have lost shrimp after a bad molt.
How often/how much of a PWC do you do? The reason I am asking is, I did a PWC every 3 weeks in my 55 and a few moths I did them monthly and I had two shrimp die (I know they aren't crabs) and I am thinking they used up all the iodine/iodide (this helps them molt and grow a new exoskeleton). But that is just my guess, since I have read other similar posts....

[fishb0ne]

They live in brackish, I don't see how iodine would be an issue.
I do a 30%, sometimes 40% PWC every week.

[roka64]

Originally Posted by fishb0ne

They live in brackish, I don't see how iodine would be an issue.
I do a 30%, sometimes 40% PWC every week.

Ok, cool, I was just checking. I assume you use a SW mix, that should contain all the trace elements needed, including iodine/iodide. Ok, so no help there.
It could simply be one of those mysterious deaths, or like you also suggested, old age. It doesn't sound like it had anything to do with your husbandry practices.

[fishb0ne]

Yep, I use Instant Ocean marine salt