Crabs always Underground? (AGAIN)

[Graz73]

OK, we've had 3 crabs since summer.
At first our aquarium was probably not that great for the crabs, and they eventually seemed to stay below the sand all the time and never move.
With the advice and information found here, I was able to make the tank conditions better.

After several months of NO activity, I carefully dug up our three crabs to see if they were still alive. Surprisingly, they were all OK! At least one had molted. I took this opportunity to make the crabitat even better and put in a better substrate mixture.

Now we've got:
• a moss pit
• a climbing feature with tiny caves in it
• various proteins, eggshells and fruits and plants for them to eat
• a couple crickets for them to eat too
• a digital hygrometer
• a large reptile heating mat on the back of the 10 gallon tank
• thermometer
• pool of fresh (declorinated) water
• pool of non-iodized sea-salt water
• I sealed most of the air holes so the humidity doesn't escape.

So now It always seems fairly warm and humid in there. The temp is usually in the high 70s and humidity in the 90s assuming those gauges are both correct.

For a while, they seemed to really like these improved living conditions. Making lots of tunnels every night and even staying on the surface sometimes.
BUT, after a month, they're now back to staying completely underground again. No tracks at all or tunnels created in the morning. Not touching hte food. Can't even hear them digging late at night anymore. Not even sure if they're alive. (But assuming they are)

So, what do I do now? Nothing? wait for months of no activity? Figure out other things to improve?

Side note: the heating mat seems to get a lot of salt water to evaporate and leave salt coated on the back wall of the tank.

[Hermiesguardian]

They may be molting. Never dig them up unless there's a flood or bacterial bloom. They can be under for several months. We then have pet sand. Keep changing out food. You can put smaller amounts. Keep changing the water. Maybe less often since it's not getting dirty.
As for the salt just wipe down the back of the tank. As for the type of salt you use I don't know if that's good for them. But someone with more experience can advise on that.

[curlysister]

As HG said, you should never dig up crabs unless there is an emergency such as a flood or bacterial bloom. Doing so can be fatal, if they are mid-molt.
What is the brand of dechlorinator and salt that you are using?

[wodesorel]

Two to four months underground is completely normal for a molting crab. Because they all came home at the same time they are likely all on the same schedule, so will be down together at least the first few times they molt. It's boring as heck!

[Graz73]

Thanks for the replies.

One of our crabs (the smallest) was bought weeks later than the others. It is the one that molted.

The other two may be molting I guess, but it's hard to tell.

I knew it was a risk to dig them up, but they had been underground a long time with not enough sand and poor quality sand. Carefully replacing the sand and other tank features may have been risky, but seems like it was worth it.

The declorinator is some Betta brand. Mentioned elsewhere on this site as being OK for use. Not sure the salt brand.

[curlysister]

The Betta conditioner may not treat all things it needs to. And you need a marine salt for hermit crabs. Here's the care sheet about water:

http://www.hermitcrabassociation.com/ph ... 27&t=92553