Hermit crab / illness

Question
One of our hermit crabs is not sitting well in his shell. We thought he was needing a larger shell, (and he did change into a larger one when it was provided, ) but we suspect that there is something else going wrong with him.  Is it possible that his soft body/abdomen could be swollen since he continues to sit strangely?  I have recently been placing their cage outdoors to enjoy the warm, humid weather.  We have not yet purchased an aquarium and heater and knew they would enjoy being outdoors.  I did add some beach sand we brought home from vacation and added it to their cage. They were also rained on while outdoors 1 evening but we cleaned their cage out. Can either of these 2 things have caused a bacteria infection or something?

Answer
Janise,   Never introduce anything to your tank from the wild like sand. Now you can do driftwood but you have to bake them at 400 degrees for about 20 mins. or stones that you can boil for at least twenty mins. The reason for this is parasites. These guys are so delicate when it comes to parasites. Ok fist we are gonna talk about their home. I would definitely go out and get at least a five gallon tank with a grated top or a ten would be better you could put quite a few in there with some nice heavy netting to climb they can be so much fun. I have about 25 in a 45 gallon tank and they are so comical to watch. I even have a couple streakers that like running around for a day or two without shells. They need many shells available to them they can be very picky and you don't want them to dehydrate. Anyway...I would recommend an under the tank reptile heater something low wattage and pick a side they because they still need a cooler side. I would also make sure they have a hermit crab salt water bath available something they can climb out of and not drown available at your local pet shop and a sponged fresh water to drink they need the salt and minerals to keep them healthy also, I keep pretty pieces of store bought coral in there because they love to eat it great for calcium. If you can't get that now you are going to have to break down and bleach scrub with salt for abrasive the tank you have them in. You need more shells if it isn't a parasite but, I think it is. There are ways to coax them you can rub lightly their abdomen with a small amount of mineral oil and try sliding him into different shells. He will grab if he or she is happy in fact while its out take a look behind their last set of legs and see if there are two black dots on either side these are gonopores and they are females. The swelling has got me worried though. This is tough thing to get rid of a parasite on the, you have to be diligent. Take it out of tank use small tank for healing possible bacterial infection too. Now the mites are usually able to be seen by the naked eye or a magnifier. They are either black or brown. You need to go to your pet shop and get melafix its all natural antibiotic made from tea trees. You are going to make up the amount in a separate container and make sure the water is dechlorinated or bottled. Soak him in it for about 10 mins three times a day for about 7 days.Run it up into the shell what we are doing is giving him a broad spectrum antibiotic and trying to weaken and drown the mites and get rid of any possiblility of bacterial infection. Check all the tank mates and boil all your empty shells decorations and such. New sponge for drinking too. I would put red light on then a nice UVA for heat low wattage since the get their calcium from what they eat. Also they love tuna fruits veggies its a trial an error thing to find out what they like but should only be put in for about 30 minutes so as to not draw fruit flies and possibly another infestation spoil them they will love you for it. This is a tough one on them so patience and persistence is the key. If you have any other questions feel free to ask no question to big or small. Good Luck, Tina