Luckily I saw your response before I got fish. I also put a towel over 3/4 of the top and the humidity is very consistent now. Before I was paranoid about them having red leg because they were very pinkish but now their colors are becoming very vibrant and they vary from bright green to brown to purple even. I am so in love with them. Since I wrote this post I have changed their set up to all water and have installed a small filter that brings the water up the back so it trickles down over the leaves like rain. It took me a long time to figure out how to do it. The frogs love it and I don't have to mist the tank now. My biggest problem now is the crickets drowning themselves. If the frogs are hungry they will jump in the water if the dead crickets are moving with the current but I have to fish them out rather soon after they down or they get all boogery looking. I also now have two gray tree frog tadpoles. They freak me out. I always think they're dead. But everything is going great with them, I'm very pleased and my paranoia has gone.