So what is this "Molting Isolation Tank" like?

The molting isolation tank (or "ISO" for short) is where your crabs go to molt in safety and privacy. Ideally it is filled with six inches of soft, moist sand. The sand should be moist enough to make a sand castle, but not so moist that it is drippy. The tank should be large enough to hold food and water dishes. To make my ISO, I purchased a 10 gallon aquarium from PETsMART for less than $10 and outfitted it with an undertank heater and a glass lid. The substrate is the easy part -- use sand. Gravel (except very fine-grade gravel) is too coarse; crushed coral and Calci-Sand® are too organic and spoil when moist. Play sand is the best molting substrate, because it is inexpensive comes in a nice big bag. For a good ISO tank, you will end up using most of your play sand, believe it or not! Fill your tank with about six inches of the play sand. Then take a jug of water and pour about one cup of water into the sand. Mix it up very well and note how moist the sand is. Can you make a little circle in the sand with your finger without the sides caving in? That is what you are aiming for -- a substrate that is moist enough that you can make a little hole like that, which is what you will do for your crabs when they need to molt. Start out with only one cup of water and if necessary continue adding water until your sand is moist and packable, not watery or drippy. Once you get that right, you are over the hardest part.

Next, add your food and water dishes. "Molting food" should be something that is rich in calcium, like cuttlebone, sand dollars, sea biscuits, or Calci-Sand®. For water, give the crabs their regular dechlorinated drinking water. I usually add a bit of saline water to the regular water, because molters need the extra salt to help retain water. You may or may not want to put some big shells into the ISO tank, just in case you have a crab that is doing a "last minute" molt and he/she needs a dark place to do it ASAP. Some crabs will be far along in their pre-molt preparations when you find them, and therefore might not have enough time to dig deeply enough into the sand. They will go "face first" into a large shell and molt there.

The finished ISO tank should look a bit bare in comparison to the crab's "living quarters," and rightfully so. After all, the crab is not using this ISO tank to climb around and play in, but for the very serious business of molting. Molting is how the crab grows; since he lives inside a hard outer casing, he cannot grow larger except in the short time while his exoskeleton is soft, namely, directly after completing his molt and before his skin hardens up.

Darkness is your friend Indeed it is! Studies have shown that hermit crabs have two molt-related hormones that enable them to 1) put off molting when the conditions aren't right, and 2) to get down to business when they are! The molt-inhibiting hormone can put into play by numerous factors, but the most important one for hermit crab owners to remember is that hermit crabs have been shown to have better, healthier molts when they are under the substrate, or in complete darkness. This is why if your molters have not been able to dig, why they will molt inside the mouths of larger shells or under tank ornaments. "Each stalked eye of a decapod crustacean contains some of the neurosecretory cells that synthesize and release molt-inhibiting hormone." (Shrimps Lobsters and Crabs: Their Fascinating Life Story,Dorothy E. Bliss) The good news is that hermit crabs also have the molting hormone Crustecdysone to help them along when conditions are right. If your ISO tank is set up correctly, when you notice the pre-molt symptoms (affectionately referred to as "PMS") in your crabs, get them into your ISO set up right away.