HCA: Hermit Crab Association

So I have 6 small/medium crabs in my tank. Its 12"x 30" and I have a 10 gallon 2nd floor. The substrate is 6" deep. And consists of straight play sand. I have a salt water bath and freshwater bath that all crabs could submerge completely into if they wanted. The temp at sand level is usually around 70° with humidity about 70% on average. At the middle/center of the tank it's about 75°-80° and 70% humidity. The 2nd level 10gal tank is usually 90° with humidity around 75%-80%. I have a UTH under the tank. As I thought that's where it's supposed to go. I also have a reptile fog machine and a misting machine. If you check the only other thread I posted in, you can see the pictures of the build.
When I first opened up this tank for business my crabs went crazy for a few weeks. Climbing and doing the crab thing. Then 1 by 1 they all went down for a molt. I didn't know that they needed total darkness during the molt. So I stuck my head under the tank and used my flashlight to track their whereabouts. Almost everyday I might add. The group molt started in sept. 2017. So it's been about 6 months. 1 came up for about a day or 2 at the 7/8 week mark and went back down for another month. 1 came up for good and 1 came up after about 4/6 weeks, stayed up for about 3-4 months swapped shells a couple times and has gone back down. Now all 3 that I know are still alive are the ones that must've been hidden from my view due to the large UTH. The other 3 have not moved from their spot at the bottom since the beginning. I'm almost positive the stress from having my flashlight shined in the face through the glass every night was too much for them to handle......lesson learned.
My question is, do I dig them up? Do I then replace all the sand? I'm pretty confident the alive crabs may never bumped into 1 of the dead ones during their tunnelling. Although, I do not smell anything bad what so ever in the tank. At one point I had a crab sized tunnel from the right side of the tank, close to the front glass, that stretched to back side then under my saltwater bath and over to the middle of the left side of the tank. I was hoping that big of tunnel would have broght up some nasty odors. It did NOT. But I am pretty sure I have a few dead crabs and I'm not sure about how to handle the extraction. What happens when one crab runs into a long dead crab deep in the sand?
Also I was wondering if the UTH actually being under the tank is a good idea. It seems now my sand is drying out. There is a layer of hard sand crust over the sand-scape. So Every couple weeks, I pout water over the top to soften it up. Im careful not to flood it, but I also try to pour a good bit in so it seeps down through.
Thanks for reading.

UTH go on the back of the tank with hermits. They are designed to give reptiles a smaller warm section within a tank bottom to warm their bellies on. We use them off-label by using a large pad to heat the air of an entire tank. With substrate more than a 1/2 inch, the heat gets trapped and the pads get too warm, easily 140 degrees on the good brands, which will cook a hermit crab. (And burn a reptile, it's why a thermostat with a probe should always be used with them.)

The crusting you are seeing is probably due to the heat causing minerals in the tapwater and substrate to crystallize. It's the same stuff that forms in hot water heaters, and to a lesser extent on faucets. Are you using playsand, or a reptile/calci sand? Playsand is the safe stuff for hermits. Calcium sand dries hard and is not good for them.

A buried crab should never be dug up as that can cause serious harm, so unless your others are up and you can dig safely it is better to just wait. A dead crab hurts nothing, as disturbing as that is to say. By this point, there is likely nothing left but shells, and because of the substrate it is very normal to never smell anything.

Hi Jimmy! I'm sorry that you are going through this. All of us crabbers know how hard it is to wait for molters.

I agree with everything that Wodesorel said. I also wanted to make sure that you are using marine salt water (to mimic the ocean).

Whatever you do - Don't dig. What is done is done. Like you said - lesson learned. We are here for you. Hang in there!

Thank you guys for the help. I've been wondering what you do for a while.

wodesorel wrote:The crusting you are seeing is probably due to the heat causing minerals in the tapwater and substrate to crystallize. It's the same stuff that forms in hot water heaters, and to a lesser extent on faucets. Are you using playsand, or a reptile/calci sand? Playsand is the safe stuff for hermits. Calcium sand dries hard and is not good for them.

A buried crab should never be dug up as that can cause serious harm, so unless your others are up and you can dig safely it is better to just wait. A dead crab hurts nothing, as disturbing as that is to say. By this point, there is likely nothing left but shells, and because of the substrate it is very normal to never smell anything.

I only use distilled water in the fog machine, the misting machine, and when I add to the substrate. The freshwater bath, I use a blend usually between 50/50 and 75% distilled/25% spring. The salt water, is 50/50. I know what're you mean about the tap water crust though. That's exactly why I don't use tap water. It's more like the sand itself after being dehydrated, it kinda clumps together. When I break it up, it turns back into dried sand.

GotButterflies wrote:I agree with everything that Wodesorel said. I also wanted to make sure that you are using marine salt water (to mimic the ocean).

I use instaocean I think is what it's called. I read somewhere that that was better to use then most of the other stuff. I check the levels with a salt water measuring tool. Sorry I can't remember what it's called. You pour the water into it and a dial will float whatever number it is.

Jimmyfingers85 wrote:Thank you guys for the help. I've been wondering what you do for a while.

I use instaocean I think is what it's called. I read somewhere that that was better to use then most of the other stuff. I check the levels with a salt water measuring tool. Sorry I can't remember what it's called. You pour the water into it and a dial will float whatever number it is.

I suspect you are using Instant Ocean. That is a good product for hermit crabs. Using a salinity meter is also a good choice.

FYI, I found after mixing the Instant Ocean according to package directions a few times that the salinity was usually right as expected, so I stopped using the meter so much, but that's just me. Since crabs mix the fresh and salt water inside their shells to come up with their own custom salt/fresh solution, I figured my salinity didn't need to be exact every time. One less thing to stress about.

Good luck and I hope your crabs turn out to be okay.