Preventing Low Oxygen Levels in Your Pond

Preventing Low Oxygen Levels in Your Pond

Carol Mund

This 3 part series concerning Dissolved Oxygen Concentration (DOC) is a summary from an article titled “Oxygen in Ponds” by Ben Helm of first post in this series discussed the occupants of the pond and how they affect and rely on DOC.  The second post in this series focused on the individual factors that can cause the DOC to drop.  Lastly, this final post discusses quick fixes to low DOC levels and also preventative methods to assure vigilance in proper oxygen levels.

As discussed earlier, low DOC levels are more likely to occur at warmer water temperatures.  And while there are precise advanced methods for determining your pond’s DOC level, visual symptoms that dangerously low oxygen levels are evident include a change in koi behavior or the koi gasping for air at the water surface.

If it’s determined there is low DOC, quick action to remedy the problem is needed:

  • Agitate the water’s surface shore term by pouring buckets of pond water back into the pond.
  • Spray a hose into and across the pond, simulating rain.  The cooler water will allow the pond water to hold more oxygen.


Obviously, prevention is far more desirable of a long-term solution than a reactive situation.  So, consider some of these options:

  • Aerate down to the bottom of the pond.
  • Allow for additional aeration for the biofilter, which will enhance bacterial colonization.
  • Clean out settlement chambers regularly.  Even when organic matter is removed from the pond, it still attracts oxygen demanding bacteria in the filter.
  • Add additional aeration during any pond treatment or medication.



  • Assume because your fish survived the host day without additional aeration that they will survive the night.  Night time is when the DOC will begin to drop so aeration is important.
  • Continue to aerate below 54°F.  Fish will settle into that deeper warmer part of the pond.  Aerating below this temperature will just mix all of those layers of water up.
  • Over stock.  This will increase the demand for more oxygen needed for the fix and the oxygen demanding bacteria as well.

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