How long should I wait before giving up?

[Shawn]

OK, so I moved into our new apartment in April, a month later I moved all of their Eco to one side of the tank and added play sand to the other half. At that time all ten of my crabs were alive and well, and immediately buried down. Shortly later I found a dead crab, one of my five smaller ones. Since then I have only seen five crabs out and about most of the time, one of which was buried down for at least two~three months. There was one other crab that came out for about two days in August or September and then reburied not to be seen again (we call him Whale's Eye Crab). The four crabs not seen lately (including Whale's Eye Crab) Who are the smallest of the bunch have not been seen since early summer at the latest.

I'm wondering what the general consensus is on how long before you can be pretty certain they are dead and buried before you dig up their remains? It's believed that the larger crabs will molt less often but for a longer time and the smaller crabs will molt several times per year but do it in about a week or two. Since these four crabs haven't been seen in four to six months is it safe to assume they're dead? I can pretty much determine that they haven't surfaced at all by the surface of the substrate and size of the holes found when the larger crabs come up from below.

[YYWW]

Thing is, just because you didn't see them for that long doesn't mean they haven't been coming up. 10 crabs is a lot to keep track of, and any of them could have gone up, then down, a couple times during late nights.
You can go digging if there are inconsistencies with your tat conditions that you need to work out. But if you know your tat is good, you can leave them be and let them surprise you.


Crabbers unite!!!

[wodesorel]

Exactly what YYWW said - especially if they are teeny tiny crabs. I have 6 in my 10 gallon, but I only ever see 2 or 3 at any one time. It also doesn't help that they've changed into matching shells! Trying to guess who is who from day to day is impossible as they will change color and size with every molt at that age. I've also had micro crabs stay down for 4 weeks, only emerging in the middle of the night for a handful of days to stock up on food and water before going right back down. The first two years I had Firefly I could count on my fingers the number of times I saw him in the tank!

[Shawn]

But the issue is, the only holes I've seen in the substrate have been large holes, the size of my four biggest crabs. I haven't seen a small hole in ages. I used to see the smaller ones when I would occasionally give the substrate a good spray down, but not since June. I'm planning on upgrading to a 55gal tank and want to wait until I know if they are all safe or dead.

[wodesorel]

How many crabs are in the tank, and how large is it? There's more of a risk of them not making it through a molt if they're crowded. There's also a good chance that if you have larger crabs, the smaller holes are getting covered over before you find them. Those holes do not last long in an active tank!

[Shawn]

At last count I had 9 in a 38 gallon tank (36x12x21) and their water bowls are raised up from the bottom so they have the entire floor area to dig and molt under without the weight of the bowls pressing down on the substrate.

[gotta-crab-em-all]

I wouldn't write them off, necessarily. I had a small crab stay underground for 4 months before she came back up, and she was fine.

Its possible the move stressed them, or there was flooding of some sort. Its hard to say for sure.