I use glad food container for humidity in the styro bators:The one incubator will not hold water at all or the humidity goes over 80 in the incubator . It stays 60 -70 humidity on to sponges not wet but wrong out. But hard to ring them out without moving eggs and opening the incubator. The other one will hold water but will not go above 50 humidity .
Each one will raise humidity 5 to 10%. Sometimes I use one and sometimes I use two. They fit tilted on one side of the turner rail.