Progress report on the solar stock tank

We've had a cold snap here and it's been a good trial run of this heater. So far I'm pleased. We have had 4 days of below freezing weather with the last 3 of those in the single digits to below zero F. And it's been windy. The first 2 days were cloudy and the 3rd was on and off. Today has been good and sunny and it's up to 10F today. It hit -15F overnight, about what it's been for the last 3 days.

Anyway, I do have to break ice in the morning but it's been maybe 1/2" or so in thickness so easily broken.  And it's only been in the access hole, the rest of the tank is not frozen.

 On the cloudy days I have had to go out and break it open a couple of times.

 

On the sunny days, it seems to stay open pretty well if I wait to break the ice until the sun is hitting the tank. 

Like I say, I'm fairly pleased with it. I foresee having to use a tank heater in really cold and/or cloudy weather, but I think our usage will be greatly reduced. Which is awesome because those things really suck the electricity!

I do need to find something else to line the access hole. I used OLD oilcloth that I had laying around and it is not holding up well. It has torn in several places and then it is icing through those holes, making it harder to get ice out. Any ideas?