Dried Out Turtle Shell
I will try to help you with your box turtle. I don’t have a lot to go on, but my suspicion is that the water soaking isn’t causing the shell to dry out as you have deduced.
Now, I don’t know where in the country you and your box turtle are living, but I suspect that you must be living in an area where you have hard water, meaning that the water has a lot of dissolved minerals in it. You may notice that when water evaporates in a bowl, for example, that it leaves a white residue or that you may notice “scale” forming inside of your drinking glasses. This scale or film is another sign of hard water, and may show up in coffee pots, in the sink or bathtub or other areas where water sits. Hard water doesn’t lather up as well as soft water.
After your turtle soaks in hard water, it will leave a white, chalky deposit on the shell and perhaps also on the skin, especially around the claws. This white deposit is what I am thinking that you are calling dry skin.
What I think you should do is to start using bottled spring water (not distilled) for your turtle’s water dish and for bathing him and see if, over a few weeks, the white deposits decrease. Apple cider vinegar solution will also help remove hard water deposits. You could dip a soft toothbrush in vinegar and gently brush the shell to see if the deposits can be removed. However, if there are any skin lesions or you are not sure about this, then certainly, you should take him in to see your herp veterinarian to have him evaluated and this “dry shell” problem looked at by a professional.
Since you didn’t tell me what kind of box turtle you own and what you are feeding him, I can’t help you there. However, your herp vet should be able to advise you about the diet and if he needs any supplements to help his shell.
Well, that’s my advice. You can have your water evaluated to see if you have hard water (most water companies and some health departments will test your water for hardness, heavy metals and microorganisms).
Need a Herp Vet?
If you are looking for a herp-knowledgeable veterinarian in your area, a good place to start is by checking the list of members on the Association of Reptilian and Amphibian Veterinarian (ARAV) web site at www.arav.com. Look for DVMs who appear to maintain actual veterinary offices that you could contact.