HCA: Hermit Crab Association

My green turbo shells are fading to this weird white/gray color. At first I thought it was because the shells kept falling into the water bowls and staying wet for too long, but today my crab's shell, which was a faded green color yesterday, is now more white. I have no idea how it would've faded that fast, or what would've caused it. Here's a few pictures: https://imgur.com/a/ycRWY The ones without a crab are what they look like before they fade, and the one with the crab is what they look like after they fade. Do turbo shells usually do this? I bought them in a big pack at Joanne's Fabric Store, but the brown-and-white shells (I don't remember the type right now) that also came in the pack has not faded, and the painted shell another crab is still wearing has not faded either. Could it be harmful to them? Could they be fading because my humidity is too high?

It's dust from the sand and wear. This also happens after boiling them in salt water. This isn't harmful to them and happens when the polished finish on the shells is worn down by the sand.

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I don't currently have any sand in my tank, and haven't for awhile. It's pure coco fiber.I I also only boiled them in dechlorinated water, because I forgot I was supposed to do it in salt water. By the time I remembered they were already checking them out so I assumed it would be fine and left them. Could the salt water in the air be doing this? I've noticed the salt water disappears faster than the fresh, but I don't know if it's evaporating or spilling out or what.

It is a chemical reaction with the shell, since shells are primarily calcium. Boiling in water - especially salt water - causes it to happen. Ccocofiber and moss is another cause due to the lower pH. Physical scrapping and the lower pH of sand will also do it. Not all shells will fade and some go faster than others. It is just one of those things about having hermits!

They soak in the salt water dishes and also if you prepared you cocofiber bricks with salt water that's another source of salt. Also I've noticed that my crabs will pick at each others shells and empty shells removing the outer layer and exposing the pearly white under layer in places. I don't boil my shells in saltwater anymore (only fresh dechlor) because I didn't like the way it dulled the shells so quickly. Also I don't see the need to continually boil them. I do when they are new before putting them in but when I clean out my shell shop and rotate the shells I just give them a good rinse.

I understand now. Thank you for the information!