Floating heater experience

[havefun]

This is my first winter for my 500g pond. I'm hoping I don't lose everything but I'm not sure. I started with a Laguna floating heater but turns out it was a bad design and leaked (I called and they said if I send it in they will send a new one back). So, I got a Farm Innovators heater. It did OK for a while, the ice eventually built up right around it and started to form underneath it. I kept it open by poking it with a screw driver every few days. Nobody told the fish they were supposed to be "hibernating" because they would always come right up and check out what I was doing.
Well, it's become extremely cold now - nights well below zero and days in single digits. I checked on it and the ice is several inches thick under the heater now.
I have plants and 7, 3 - 4 inch commets in there (I removed my oranda/fancy and fancy to my basement a long time ago).
What should it do? I'm assuming if I leave it I will have 7 dead fish next spring? Does anyone else rely solely on a floating heater to keep a hole open? What has been your experience?

Thanks for any help!