system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do fish survive in iced-over lakes and ponds?

I was under the impression that fish still needed to have their water exposed to the air if they want to breath. When I was a kid I had a fish that died because the bowl was covered. How do fish survive in lakes that are completely iced over for the entire winter, won't the fish use up all their air, and then die before the lake thaws in the spring? Or does the air somehow seep through the ice?
gpt
While the lake may be frozen the rivers that flow in and out are still flowing, if not on the surface then at least under the ice. This will bring in oxygen. Also lake ice isn't one solid chunk there are cracks and breaks in the ice that will allow gas exchange.  

Plus fish are cold blooded, so in the winter their metabolism slows way down, they don't swim around as fast, if at all, and so require less oxygen. Many fish just find a place out of the currents on the bottom of the lake and sit out the winter.