I have a hova-bator incubator, I just bought a fan to add to it. My question is should the fan push air toward the eggs or pull air.The fan is from the Hova-Bator website, but it does not say in the instructions which way the fan blows. It mounts on the top, also the way I hooked it up to the power, the fan turns on with the thermostat. Does the fan need to stay on or not? Thanks ya"ll