Pond fish need a break too! During the winter months, it is an absolute truism that pond fish do in fact hibernate. When the fish in a pond reach this time in the season, their metabolism slows with the cooling of the pond water. This is natural for them (more so for the Koi) as true pond fish are cold blooded creatures. Most of their time will be spent near the bottom of the pond, moving with as little frequency as possible. As a pond owner there is not much to do with them at this point, however, there are a few important winter items to consider.
Do Not Feed the Fish
During their hibernation period’s fish should not consume food at all. Too often, an oddball day occurs where the pond water warms a bit with a spell of unseasonable weather. The fish get a little active around the surface of the pond so their owners feed them. The net effect is when temperature returns to normal the fish begin to float on their sides on the pond surface in an attempt to process the food that their bodies cannot handle. It is acceptable to feed the fish when the water temperature is above roughly 65 degrees. There are spring and autumn diets for pond fish that should be fed while the water temperature remains at or below 75 degrees. These special diets contain low amounts of protein and are easier on the gut of the fish. Again, in water temperature below 65 degrees, don’t feed those fish!
The other item for winter is the propensity for the pond to freeze over. Although the fish are hibernating, they still require oxygen. When the water in a pond is covered by ice, oxygen is trapped out and carbon dioxide is trapped in. It is critical that if you live in an area where a pond could potentially freeze over, you take steps to ensure this does not happen. In areas where the temperatures are not below freezing often, it is a good idea to leave the pond pump running. This will help it not to freeze over and it keeps the water oxygenated. Also, it is a good idea to purchase a pond heater which will ensure at least a small portion of the pond will remain open. Most heaters designed for ponds (not stock tanks) operate on low amounts of electricity and are well worth the investment.
For most pond owners, winter is a simple time! The only thing the fish in a pond will require is oxygen and rest. As long as the fish remain unfed and the water is unfrozen, expect to see healthy, active fish come late spring!