koi winter survival guide

Unfortunately, zone 6 Winter weather is not conducive to raising koi in the long run. I often see the cumulative effects catch up, or a fish is slightly off 1 Summer and just doesn't have the constitution to make it to Spring

It is sad because we often see people making avoidable mistakes due to misinformation or a lack of knowledge. Please take the time to read over this page and give you fish every chance to make it to Spring
Keys to Success:
  • Prepare the fish during the Summer + Fall
    This means that the fish should be very well fed and kept in good conditions during the summer season and fed as long as possible into the Fall. High quality foods should be offered

  • Greenhouse or Net Covering
    Putting up a covering in early October is a great idea. It immediately warms up the pond, prevents any leaves from getting in and it extends the season allowing you to fed the fish longer. Huge benefits for little cost. In Toronto we recommend that the greenhouse not be removed until the first week of May

    A net should be used in heavily treed areas to make the Fall closing that much easier

  • A Proper Pond Closing
    Closing the pond properly is of course paramount. See extensive details below

  • Winter Monitoring
    Check to make sure your bubbler and deicer are functioning and remove some of the snow off of your pond. The latter is not necessary of course if you have a covering

    A heavy snow covering can cause "winter kill" by putting the pond in darkness and the string algae into respiration mode. This consumes the oxygen, creating anoxic conditions and killing fish, the larger specimens succumbing first

  • Spring
    Remove any ice as soon as possible - without smashing it. Heat of fusion is the energy [79.2 calories / gram / C] required to melt ice - without any temperature gain. When it warms up in late March and April, instead of warming the water, the energy goes to melting the ice first. This is significant, almost 80x more energy than warming liquid water which requires only 1 calorie / 1 gram / 1 degree C rise. Remove the ice and your water warms up much faster, and also do another big water change and add some more salt


pond closing procedures

A proper pond closing prepares your pond and its inhabitants for the Winter ordeal. A good checklist is as follows:
  • Net out Leaves and debris
    Rotting debris can increase the B.O.D. The quantity of dissolved O2 required to perform the breakdown of organic matter. This process is predicated on temperature creating low oxygen levels and potentially producing toxic hydrogen sulfide. Try to net all of this debris out

  • Large Water Change
    Refreshing the water, removing nitrates and organics are a good reason to perform a 30 - 50% water change late in the season. These large changes can be done at this time of year because the tap water temperature and the pond temperature are fairly equitable - so no large shift of temperature occurs. Remember, use water conditioner or this size of change will kill your fish

  • Increase Salinity
    The addition of salt eases the active osmoregulation process by reducing the amount of salt lost and making it easier to recoup. This energy is therefore conserved and can be used for survival. Additionally, sodium and chloride are essential for ion exchange through the gills. Adding 1-2 lbs. per 100 gallons is an advisable rate. Urban Pond Myth would suggest that this lowers the freezing point, so don't have any salt. However, a 0.20% level would only lower the freezing point to 31.8 F, hardly of consequence

  • Deicer and Bubbler
    Deicers are floating thermostatically controlled devices that melt ice. Remember, a 100 watt unit might be on 3x longer than a 300 watt unit so your hoped for energy savings is nullified. We recommend using at least a 300 watt unit

    Aeration is also key, but you don't need as much as you do in the heat of Summer. Cold water holds more oxygen, and the fish breath less in cold water. However, if the whole pond is covered in ice, there is little surface area for O2 absorption. Affix an airline to your deicer and let it hang about 1.5 - 2 feet down. In the depths of Winter you will easily be able to see if your aerator is working okay