Pond Winterizing

Start of Fall

As water temperatures begin to drop, you should start to decrease the amount of food and frequency of fish feeding. If you are feeding daily, drop back to every other day, then 2-3 times per week until you stop completely when the water temperature reaches 50°F.

Start your fall beneficial bacteria treatment. If you have had problems in the past with fish disease or your fish “look sick”, treat the pond for parasites and bacterial infections when temperatures are above 50°F. Some find it beneficial to add pond salt for the protection of the fish. Just remember that pond salt is only removed by water exchanges and may disturb the growth of aquatic plants.

It is recommended that the pond be covered with a net to keep out the leaves and debris that drop from the trees as the fall continues. Rather than stretching the net flat across the top of the pond, create a tent shape so that the leaves roll off the net to the side of the pond. This will make it easier to gather the leaves for composting and keep the net from sagging. The net should be left on until all the leaves have fallen from the trees and you have picked them up from the yard. Remove the net before the first snowfall.

As the foliage on the hardy plants begins to yellow and die back, trim it off so that it does not decay in the pond. Floating plants and tropical plants can be left in until the frost has killed them and then promptly discard and composted. If you plan to winter any tropical plants indoors, be sure to bring them in before the first frost.

(Additional information follows at the end that indicates which plants are hardy and which are tropical.)

If you plan to bring your fish in for the winter, weigh your options carefully. Larger fish are better left outside since they will require more room inside than smaller fish and usually have a large enough body to store energy for the winter. Fish moved inside will need to be kept inside until water temperatures rise enough to move them back out. This can be well into spring in our area. Also, fish inside will need more care throughout the winter than those left out.

Inside you will need a holding tank, pump, and filter. You can use your filter and pump setup from outside, provided it is not too large. The best place for your indoor tank will be where the temperature of the water stays between 50°-60°F. This will keep the fish's metabolism slow but not dormant. Before temperatures are too low, bring some of your pond water in for your indoor setup if it is good quality. When filling with tap water, be sure to de-chlorinate it or let it sit for one week before putting in fish. Test the temperature and pH inside and outside to ensure that fish are moved into water with the same or similar levels. Test the water and keep records throughout the winter for pH, ammonia, and nitrite. When everything is set up inside, you can begin moving the fish inside. Try to move them on a day that the water temperature in your outside pond and inside pond are within a few degrees of each other. This will avoid putting the fish under unnecessary stress. Be sure to cover the indoor tank with a net. Fish, especially Koi, will sometimes jump after a move. It is a good idea to keep this net on all winter. Continue to check your water chemistry on a regular basis throughout the winter. A partial water change may be necessary if you notice a rise in ammonia or nitrite. Feed your fish minimally to keep ammonia levels in check—once a week should be plenty under ordinary circumstances.

In the spring, wait again until your indoor and outdoor water temperatures are within a few degrees of each other before moving the fish to their summer home. Do your spring cleaning on the pond before you move the fish outside. It is a good idea to test the outside water for pH before moving the fish. Ideally, the pH should be the same in both the outdoor and indoor tanks to move the fish. Be sure to dechlorinate the tap water after cleaning the pond. Your biological filter will already have a head start since it has been running all winter. Return both the filter and the pump to the pond when you move the fish. Increase feeding as the temperature rises until you are at your normal feeding level.

If you plan to over-winter tropical plants indoors, remember to remove them from your pond before the first frost. They must be kept moist but not necessarily submerged in water. Trim any tall foliage.

As the foliage on hardy plants turns brown and begins to decay, remove it from the pond. Avoid cutting stems that are hollow such as Zebra Rush or Corkscrew Rush—just leave the dead foliage on these until spring. Cutting them sometimes leaves an opening for water to travel into the plant and to the roots where it rots. Outdoors they can be dropped to the deepest part of your pond or buried in the ground beneath the ice line. If your pond is not deep enough for plants to sit below the ice line, bring them to a basement or garage where they can continue dormancy but will not freeze. Be sure they are plenty wet when you put them down for the winter. Hardy plants can be kept moist by placing the plant in a tray of water or layering the top with wet newspapers and sealing in a plastic bag. Be sure to check throughout the winter to be sure the plants are staying wet.