Q: What are winter fish kills and how can I prevent them? – Alison in Illinois
Winter Fish Kills, They Don’t Float With Us!
You’ve waited all Winter long for the ice to melt over your water garden so you can run your waterfalls and enjoy your finned friends. Instead, you find your fish floating at the ponds surface, victims of a winter fish kill. What is this phenomenon and how can you prevent it?
Make Some Holes
When a layer of ice forms over the surface of you water garden, it essentially eliminates any transfer of air to or from your pond’s water. What this means to you is that, as debris decompose and your fish consume oxygen, byproducts are produced in the form of gasses that are toxic to your pond’s inhabitants. These gases are trapped under the ice and cannot escape; fresh air from outside the pond cannot reach the water either and so begins the process of the winter fish kill. Keeping a hole in the ice will allow the bad air in the pond to be replenished with good air. Some pond guys and gals use pond De-Icers to maintain an open hole, but many more rely on their aeration systems to do the job.
Pass The Bubbly
We’ve discussed in our past blogs the many benefits of aeration in your water garden. It circulates the water in your pond, infusing it with oxygen which is beneficial to your bacteria and fish. The constant bubbling produced by an aeration system will also keep a hole open in your water garden in the winter months, ensuring the release of those harmful gasses.
Being Supercool is SO Uncool
You have all heard concerns expressed in our past blogs in regards to “supercooling”. While this is a rare occurrence, there are a couple steps you can take to ensure you don’t overdo your winter aeration. When the cold weather comes, move your aeration plates to a shallower part of your pond. This will maintain a warmer layer of water for your fish to retreat to if the water does get a little too chilly. Furthermore, if you have a multiple plate system, you can run your water garden on just one plate for the winter. This will ensure that you have an open hole in your ice and should provide sufficient air supply to your fish as they require less oxygen during these times of decreased activity.
POND TALK: What type of aeration do you use in your pond? How have your fish fared over the past winters?