Dear Blue Lobster:
Just two days ago I purchased a Watermelon Fiddler at a local pet store. Currently, it is lying on its back motionless. I have read your posts on molting, and I would like to know how long it typically takes for a fiddler crab to molt. How long I should wait before I consider it to be deceased? It has a strange arm-like structure rising from its underside. Thank you for your time, I appreciate your advice and love your site.
Dear Gentle Sir:
I regret to inform you that your crab has died during a bad molt.
Death by ecdysis is a common way for crustaceans to bite it. One of the risks of ecdysis is that the process may leave the animal in a lethal, half-molted state as your crab was. The only way to ensure the molt goes as well as possible is sitting, or closely monitoring the molting process.
While sitting your crab, you'll need a notebook and pen, a camera (digital or otherwise), some sort of audio recording device, a flashlight, fresh bottled water, and an intimate knowledge of the molting process. You also can not molt yourself while sitting for your creature during its molt.
Your best bet if the crustacean appears distressed is to remain quietly watching it; molting is a slow process and reaching in with the surgical scissors too soon is just as harmful as doing so too late. This is the classic "do no harm" vs. "don't just sit there, do something!" dichotomy.
All difficulties aside, here are some general tips for molting:
Turn the tank off or, if they're set to a dimmer, down. Your cray will need to relax during the molting process.
Keep inquisitive or predatory creatures away during and after your cray's metamorphosis. They will smell the cray's condition and attack.
Do not offer food, as the cray won't eat during the molt and any food in the tank will spoil.
Keep your filtration system turned down as the suction can crush your soft cray faster than you would be able to rescue it.
Play nature music. Underwater recordings mimic the birth process which is similar to your cray's molt.
Good luck and remember to watch our for that "third arm" that is the telltale sign of a molt gone bad.