I am new to incubating and just purchased a LG circulated air bator used for $25. It is a great shape and the temp is holing steady between 99-100. However my humidity is all over the place. This morning when I got up it was 29% and after I added a little bit of water it jumped up to 70%. I opened the ventilation holes trying to get the humidity down. How much water are you supposed to add at one time? I see some people using sponges. How does that work? Any information will be greatly appreciated.