koi winter survival guide

Unfortunately, zone 6 Winter weather is not conducive to raising koi in the long run here in Toronto. I often see the cumulative effects of this catch up, or a fish which has been sick or is slightly off one Summer 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. I usually feed my fish until at least mid November here in Toronto

  • Greenhouse or Net Covering
    Putting up a greenhouse covering in early October is a great idea. It immediately warms up the pond [potentially 3-4 C] and prevents any leaves from getting in. This of course extends the season allowing you to fed the fish longer - about 1 month or more when you consider both Fall and Spring. 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 [hand netting a lot of leaves isn't easy] to minimizing the number of leaves at the bottom of the pond

  • 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

    Super Cooling
    Another real problem is Super Cooling / Chilling. If conditions are right [wrong!], their is a potential for the water to go below zero and still remain a liquid. A deeper sheltered pond has benefit here where the water will hopefully remain at least 2 and potentially 4 degrees centigrade at the bottom [warmed up by the surrounding soil]

    The conditions to watch out for are a pond with no ice covering, a very quick cold snap and strong cold wind. This can cause the pond to start mixing and "turning over" while being chilled by the wind. If the water goes below 2 C you may find fish isolating and then floating when near death. Generally removing them from the pond and warming up slowly will save them
    More info is available on super cooling in our Pond Blog [see Jan 22 Freezing Fish]

  • Spring
    Remove any ice as soon as possible - without smashing it. Heat of fusion is the energy [79.2 calories / gram] required to melt ice - without any temperature gain. When it warms up in late March and April, instead of warming the water, the suns energy goes to melting the ice first. This is significant. Instead of warming the water @ 1 calorie energy / 1 gram of water / rises 1 degree C almost 80x more energy is used to melt the ice ! Remove the ice and your water warms up much faster, and performing another water change and checking salinity is also prudent

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
  • A net is vital in heavily treed areas
  • This container protects the aerators from the elements
  • A cover usually prevents any ice from forming