When you say tub I am assuming that you are using a rack system. I had a similar problem in the winter in NY, so what I did was first of all is switch the substrate from paper towel to aspen bedding, next every time I change water I used warm water which will fog up the front of the tub pretty nicely, then I will mist substrate 3 days later which happens to be the day before I feed. This seems to keep them happy for me and shedding in 1 piece. Hope this helps.