I am not a chemist, but Crucian Carp manage some chemical trick to convert food into oxygen (the reverse of what you're saying): https://www.sciencedaily.com/r

I am not a chemist, but Crucian Carp manage some chemical trick to convert food into oxygen (the reverse of what you're saying): https://www.sciencedaily.com/releases/2006/08/060825103548.htm https://www.sciencedaily.com/releases/2006/08/060825103548.h... (Truth be told, Carp in general are so resistant to winter, I wonder if most carps have this trait in some amount)