Illustration of No Aeration Versus with Airmax Aeration
Pond & Lake Q & A
Q: I lost all of my fish after the winter. We love to catch fish in the pond and now we have to start over! What happened? And is there anything I can do to prevent this from happening again? – Alfred of Michigan
A: My first thought when I read this question was, “They don’t have an aeration system”. And after speaking with him, come to find out, he didn’t. This is usually always the case during a winter fish kill. Everything seems to be going just fine when all of a sudden one morning you wake up to discover a wave of fish floating on your pond’s surface. This is not a pretty sight, nor is it any fun to clean up. So what causes fish kill and what can you do to prevent it?
What Causes Fish Kill?
During the warmer months of the year a pond with no aeration will contain oxygen towards the surface of the pond. This is because there is an oxygen transfer from air to water at the pond’s surface. The bottom of the pond, however, will contain very little or no oxygen; Certainly not enough to support fish life. Also, the toxins associated with fish waste and other organic biodegradation tend to sink and stay at those lower depths of the pond, polluting the already oxygen-starved water. This unfortunately, condenses your fishes’ habitat area and forces them to live towards the surface of the pond.
There is also a difference in temperature from the bottom of the pond to the surface. The bottom of the pond will be colder than the pond’s surface. The reason for this is because the sun will heat up the surface of the water and since cold water is denser than warmer water, the cold water will fall to the bottom. This difference in temperatures can be quite dramatic at times. Have you ever jumped into a pond and felt the brisk cold water towards your feet? This is the thermocline border. This dramatic change in temperature can cause your fish to stress as they travel from a warm temperature to a cold temperature and back to warm. This stress can lower their immune systems.
During the colder months of the year, the oxygen as well as the thermocline will actually flip. All of a sudden the colder water containing no oxygen will mix with the warmer water with oxygen. As this mixing occurs, the fish are left with few places to go for oxygen and they will eventually suffocate.
Another issue during the winter are toxic gasses. As bottom organics (grass clippings, leaves, trees, twigs, fish waste, etc.) decay, they will create toxic gasses. When ice covers the pond’s surface, these toxic gasses are trapped underneath the ice and will cause a fish kill.
Preventing Fish Kills
Using an Airmax Aeration System is the single most important way to help prevent winter fish kills. The reasons are simple: With an Airmax Aeration System, a compressor sits on shore and pumps air down to a diffuser on the pond’s bottom. This air forces the cold water containing no oxygen to the pond’s surface. This water, because it is denser, will fall back to the pond’s bottom. This cycle will repeat and create a convection or current within the water column. This will fill the whole water body with oxygen as well as maintain the same temperature level throughout the pond (see illustration on left).
Also, during the winter months, when ice has covered the surface of the pond. An Airmax Aeration System will keep a small hole open in the ice to allow those toxic gases to escape.
The Bottom Line: Having aeration will help reduce the chances of fish kill. Also, remember that this is one of many benefits of having an aeration system (Refer to this blog post for the other benefits of aeration).
Filed under: Aeration, Fish Kill, Pond & Lake | Tagged: Aeration, aeration system, aeration systems, aerator, aerators, airmax aeration, airmax aeration systems, fish kill, fish kills, winter fish kill
I thought I read from one of your emails last year to NOT leave my Aeration System on during the winter.
I have milfoil in my pond. I was told to use Weedtrine-D, Cutrine-Plus and Cide Kick to eliminate this. How much of each and do I spray the surface or inject below the surface? Please advise. Thanks, MONIKA
Mark,
You may have been referring to my post on Super-Cooling, which happens extremely rarely and only will happen in super cold climates such as the US/Canada border and further north. Either way, during the winter, we still suggest to run the aeration system. In the Super-Cooling post though, we talked about how to have aeration running during the winter in those super cold climates. Hope that clears things up!
Monika,
Weedtrine & Cutrine should work, but I would highly recommend using Pondweed Defense instead. Pondweed Defense has no water use restrictions where as Weedtrine has a swimming, irrigation and human/animal consumption restriction for up to 5 days. Also Pondweed is in most cases less expensive as well. When using Pondweed Defense, use 3 quarts Pondweed, 4 oz Cide-Kick and 1 gallon of water. This will treat approximately 2,500 sq. ft. of milfoil.
Hopefully this helps.
Hi,
I have a 1acre pound that is about 14ft deep. I have bass, bluegils, cats and crappies. Last sept. for the heck of it i tried some rainbows. Living in wisc. I figured my water temp. would be ok except in july and aug. might be a problem. I had an algae bloom which i sprayed w/ cutrine plus this spring. Then i read where it couldbe harmful to trout. A month had passed and i saw no dead trout. However last week it was 90 plus here a few days and i’m finding dead trout. Do you think its the hot weather or the cutrine. My pond is only well feed w/ run off….I haven’t ran the well much this spring/summer my water level is staying good. What do you think
Kurt,
To me it sounds like the warm weather. Trout are definitely not a fan of the warmer weather. If it was the Cutrine-Plus is would’ve harmed the trout by the next day. Any copper-based product is not recommended when treating ponds that contain trout, however, if the carbonate hardness of the water is above 50 ppm your trout will actually be fine when treating.
Hopefully this helps.
Thanks for the response. One last thing, with my pond being 14ft deep ifigured it would stay cool enough in the deeper part. Won’t trout find that area. I have 2 aerator stones running at about 8ft because they won’t work pass 10ft. Could the aerators also not be putting enough O2 in the deeper part.
thx
Kurt,
Your definitely thinking right. The O2 levels down in that 14ft area are still low and making it inhabitable for any fish, let alone trout. If you can get it down to that 12ft area you may be better off. What type of aeration system do you have?
i have a linear air compresse, i think………that i run 2 stones off
of………………i just find it hard to believe that my water temp down
that low isn’t in the 60 degree range. i’ve pasted some info on my aeration……..what aerotor can do a good job in that 13 to 14 ft area
Linear Air Compressor
Low cost! continuous duty air compressor Runs on 96
watts very efficient with few moving parts. A great value and will provide
many years of service.
Kurt,
Your compressor is only 96 watts? That doesn’t sound right. That seems like a very small compressor. Ours are anywhere from 350 to 600 watts.
Is there a brand name on the compressor. Do you have a link to a website that contains the compressor. Maybe I can take a look at it to see if that is really what you need.
The other issue you run into is that the water temperature may be 60 degrees but if oxygen levels are too low then the fish won’t go down there.