Try not putting anything in at all. If that brings the humidity too low, you can get a small jar (baby food or something) and cover the top partway with foil until you get the right humidity. The deeper the jar, the less often you have to refill it. It's the surface area that determines humidity.Any tips on getting and keeping the humidity at 30? We have a small sponge in there that is damp and it's staying around 50. Just a smaller sponge?