Like the other good folks above have said, it's due to low humidity/dehydration. Do you cover the lid of the tank? If not, I'd cover a good part of it with foil to help keep the humidity up.
Other than that, get a rack/tub and stop fighting with the fish tank.
Lucifer Sam, Siam cat...
Always sitting by your side,
Always by your side...
That cat's something I can't explain...