depends on how the humidity/temp goes in the tank. takes a few test to get it right. dont cover it up all the way for the first time, unless you have and temp control that shut off by itself when temp is high enough. it's really easy to get over heated. i cover like 80% of my grated one with plastic wrap and put lights on the uncovered part. works fine for me,right now is around 65% moist(haven't mist it this morning), room temp is 62 around 80 degree in the tank with both light and under tank heater on.