Avoid spreading aquatic invasive species when winterizing your water garden
Help to protect the environment from unwanted aquatic invasive plant releases by thoughtfully preparing your pond for winter. Pond winterizing also helps to maintain a healthier ecosystem for your fish.
All gardens require maintenance. Water gardens especially require winterization in northern climates like Michigan. Removing debris and non-winter hardy plants from your ponds will help to reduce the nutrient load in the water as these plants decompose. Decomposing plants also reduce oxygen levels and can emit noxious gasses which can add stress or kill your fish and other aquatic residents of your pond.
One of the things Michigan State University Extension suggests is to manage your plants. Cut back the vegetation of those hardy plants that will be overwintering in the pond. Other plants that are fast growers should also be thinned. Move any plants that are in pots on the pond shelves deeper into the pond to protect them from freezing. Tender or tropical plants are removed. After removing live plants from your water garden, discard them responsibly. Never discard water plants or animals by putting them into other bodies of water. If the plants are invasive aggressive growers or you have snails, do not compost your plants. Compost bins can harbor invasive plants allowing them to root and provide shelter for snails and their eggs.
If you plan to winter over your tropical and tender plants or fish, you need to bring them in to an indoor holding tank fitted with a filter, aerator and appropriate lighting. Plan to provide 12 – 16 hours of light per day.
Clean out the bottoms of your ponds and fountains. This will remove large debris, sludge and decomposing bits of plants and sticks. If you continue to provide filtering and aeration in your pond you will reduce the build-up of muck and maintain higher dissolved oxygen in the water for your fish through the winter. Cover the pond with leaf screens or netting to protect the pond from new inputs from falling and blowing leaves and grasses.
Stop feeding the fish when water temperatures reach 45 degrees Fahrenheit. Even if the fish appear active, they are entering a dormant state and will not be able to adequately process any food given to them. Keep at least 10 percent of the surface of your pond open for gas exchange. If you have a larger pond and use it for winter sports allowing it to freeze over completely you will need to remove fountains, turning off or your pumps and filters.
Set heaters, aerators and pumps up higher in the water on a platform or shelf of the pond to allow the water temperatures to stratify. This reduces stress on the fish from water temperature fluctuations. Continue to monitoring your pond to ensure that water levels and pH remain stable through the winter. If you have removed all of your plants and fish in smaller ponds and fountains drain and cover the pond as needed to maintain safety.