Warmer water stays near the bottom of your pond, fish will congregate here in order to stay warm through the winter. hanging around toward the bottom of your pond. Your fish are going to stay where water is the warmest and they can expend the least amount of energy to survive winter. Fish will often huddle together at the pond floor to also improve warmth and for safety.
Sometimes your fish may come up towards the surface during the winter while they're supposed to be sleeping. This could be caused by a number of reasons. Firstly, fish don't truly hibernate, they enter a period of relative dormancy known as torpor. This means while they do have incredibly reduced movement and activity, they aren't fully asleep and their internal systems are still functioning fairly normally. It's normal for fish to sometimes 'wake up' from torpor and move around temporarily, either to search for food or warmth, or because they've been disturbed in some way. If your fish are all congregating around a hole in the ice near the water's surface, this means they may not have enough access to oxygen. In this case, it may be a good idea to widen your hole or create more.
