I got an incubator for $50 yestereday. It was the Little Giant Still Air Incubator. It has 6 water channels on the bottom. Do they need to be full at all times? Should they be full any time? How full should they be? There also are 2 plugs at the top. They say I should take one off, and then the other, but they don't tell me anything else. What time should I be taking these off? I'm going to be hatching duck eggs.