Cool. We have millions of plastic eggs around here I could fill up for heat sinks. Good idea.
I added 1/2 T of water when the humidity dropped to 20%, and it's at 52% now, which is more than I think I want. It only came with one of the red plugs, the previous owner having lost one. Looks like I need to come up with something to use in the second hole. I'm a little shocked about the humidity as my house runs at about 45% naturally.
It's holding its temp beautifully at 100, but I wonder how it will drop overnight as the house cools slightly.
I have misplaced the plugs before too. I used tape over the vent holes. I have also laid a towel over my incubator. This is when our power went out.