I'm going through a tough little bit with my crab buddy right now, and was hoping there would be someone on here familiar with semi-aquatic and brackish tanks like the perisesarma bidens live in. So far I've raised him without any issues on his own in a very small tank, but recently I was sick and delayed cleaning his tank. He molted while the water was down to at least 1/4th its usual level(around 3 weeks between cleanings) and ever since I cleaned and replaced him he's been strange.
First of all he's seemed really weak. When I first replaced him he fell on his back and struggled to get back up. I thought this was just his new shell, but as days went by he grew weaker. He lost two limbs on one side(They were simply sitting in the center of the tank. They did not appear to get caught on anything and he did not appear to be eating his own legs instead of his food, they remained untouched. After this I noticed him fall onto his back off of a rock and struggle to get up all on his own, now his legs appear stiffer(One back leg on one side is simply hanging, not being used at all.)
I've just cleaned his tank again, cleaning the soil very thoroughly this time in case it has to do with algae. I've been feeding him Hibari Crab Cuisine and API Bottom feeder, I was told on a guide to feed him fresh vegetables but he has never eaten them when I provided them. It is worth noting that before this recent clean he was not eating any food. The food began growing a spherical yellowish orb of some algae before I cleaned it(I now have a baster to remove uneaten food, something I had not needed before) and his lost legs grew this same algae.
I know that these crabs aren't very commonly kept, and this forum isn't exactly a specialist forum, but if anyone has any guidance I'd appreciate help!!!
EDIT: Wanted to provide some pictures.http://i66.tinypic.com/20po3u0.jpg