Pond Maintenance - Fall Clean-Up and Winter Prep

Here are some tips to help transition your pond as we slide into fall and winter! Please keep in mind that overwintering your koi or goldfish outside is only recommended for ponds with a minimum depth of 18-24” to keep the pond from completely freezing solid.


Start by scooping/straining out all the leaves and debris floating on and in the pond with a net, as well as debris resting at the bottom of the pond. Having too much decaying organic material in your pond can lead to a quick and significant drop in pH, not to mention an increase of ammonia, which can and will quickly lead to very unfavorable water quality and fish stress. Pond nets that cover the surface of the pond are available (like these Laguna Protective Pond Nets), and they do a great job at keeping leaves, pine needles, and falling debris from collecting in your pond. Again, this prevents all those items from breaking down and dirtying up your water, making cleanup next spring MUCH easier. And BONUS! netting your pond can help keep your fish safe from Blue Herons as they migrate through Michigan. Unfortunately fall is a common time to lose pond fish to these stealthy, beautiful birds. You will want to pull your net off the pond and store for the winter after the leaves have fallen and the threat of snow begins.


As the temperatures drop in September and October consistently below 64 degrees, it will be important to start cutting back the amount of feedings and transition your fish to a koi/goldfish food that is wheat-germ based, making it easier for their bodies to process and digest as their metabolism slows down. We recommend Blue Ridge Cool Water Wheat food or Sera Spring & Autumn Cool Weather food. Be careful not to overfeed! Once the water temperature drops below 54 degrees consistently, it will be time to stop feeding altogether for the season, as their digestive systems become dormant due to the increasingly cooler temperatures. If you don’t have a thermometer in your pond yet, Laguna makes a very handy floating pond thermometer that you can use in every season (except maybe the middle of winter in Michigan:).


At the start of September, you’ll want to discontinue fertilizing your plants. As the temperature continues to cool and the plants start to turn yellow, cut all perennial water plants, such as cat-tails, lotus, hardy water lilies, arrowheads, etc, down so that they are about level with their pots. If you have annual plants, remove them completely. The goal is to diminish the amount of organic material (dead leaves, flowers, plants, etc) that would otherwise end up deteriorating at the bottom of your pond during the winter. After the leaves and stems have been removed, place the pots in the deeper end of your pond (if they are not there already). The purpose of this is to keep the roots of the plants from freezing during the winter and likely killing the plant. 


While it’s still ‘warm’ right now (or at least, not freezing yet!), it would be a great time to do a water change. We like to add Microbelift Autumn/Winter Prep after this (and be sure to still add a pond dechlorinator as well if you are using city water). Autumn Microbelift contains enzymes and cold weather bacteria that help break down debris in the pond faster, and the water change will help your water quality be at it’s best while you prepare your pond for the coming winter season.


Every pond system is unique, and there are several ways to overwinter your pond...especially when it comes to running pumps and filtration systems. Most pond owners in the cold Northern areas choose to discontinue use of the external filter throughout the winter season. There are a couple of reasons for this. First, with everything living in the pond becoming basically dormant, there is little need for the use of an external filter, as wastes and organic buildup are not being produced like they are during the warmer months. Second, if there is not enough water volume flowing fast enough through the hose and filter, the water can freeze within the filter components and cause some serious damage. If you do choose to discontinue the use of the filter box or canister, unplug it, drain it, clean it out well, and store it out of the elements to keep it protected. Also, disconnect any waterfall and/or fountain features and keep them off for the winter.


If you use a UV sterilizer, disconnect it, clean it and store it indoors as freezing temperatures can damage the light bulb within the filter. 


During the coldest parts of the winter, Michigan ponds will partially or completely freeze. Fish can be safely overwintered outside as long as there is a minimum depth of 18-24”, and an unfrozen spot at the surface that is at least 6” in diameter. Keeping an opening in the ice at the surface of the pond to allow for adequate exchange of gasses between the water and the air. This is the most important aspect of overwintering fish; if the pond freezes over completely the fish will suffocate due to lack of oxygen. There are a few different ways to keep this area from freezing:

  • Continue using the pump (that was disconnected from the filter and/or waterfall) throughout the winter. Clean the pump of any debris that has accumulated on and in it, making sure to clean the impeller and impeller housing to help the pump run as efficiently as possible without any obstructions. If kept mid-pond depth but pointed up, it will keep an area at the surface agitated enough that the water shouldn’t freeze (don’t keep it at the bottom of the pond where the ‘warmer’ water will stay, but around a 24” or so depth so it doesn’t freeze over). 
  • Use a floating pond de-icer to keep an area open at the surface. The de-icer will not keep ice from forming across the whole pond, but it will keep a large enough area open to allow for adequate gas exchange to occur.
  • Using a pond sized air pump will help agitate and oxygenate the water enough to keep an opening in the ice if the winter is on the milder side. If a cold winter is expected, however, the use of a water pump or a de-icer in addition to the air pump may also be recommended.

We hope you have an enjoyable end-of-summer pond cleanup! Please contact us with any questions!

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