Pond Boss Forums GENERAL QUESTIONS Help Winter Fish Kill with Aeration?

I am going over to check out a new friend's pond tomorrow. She had a big fish kill this winter. I told her that it was probably caused by the heavy snow we this winter and her pond being covered with no light getting in. She stated that her aeration ran all winter and she had open water. I will take pictures and try to post more details tomorrow after I get there, but any ideas what would cause this in a Michigan lake? I have no more details, but just want to see if there is some obvious things I should be looking for when I get there.

Water got too cold maybe?

How big is the pond?

Where was(were) the diffuser(s) set?

How much air flow?

Were the diffusers run 24/7?

A client had to have his pond completely restocked. His dad was keeping an eye on the house one winter (they were gone a month) and thought that the aeration system didn't need to run during the winter, so he turned it off. Expensive mistake....

Post what type and age (size) fish died.As stated above anything you can find out about the system (cfm,diffuser type) placement etc will help.Also age of pond and amount of potential organics in it leaves etc. Last chemical application if any, dye used ? These items would be a good start to get an answer (s)

I had a twin bottom diffuser aeration system running 24/7 when a three year drought shrunk our 2 acre pond to 1 acre and caused a partial fish kill - not enough O2 for 2 acre worth of fish.

Bottom diffuser systems are questionable fish kill protection in extreme conditions IMO.

Pond currently ~3ft low.
I now have a Kasco 1hp surface aerator running 24/7 and if conditins worsen I'll kick in the bottom diffuser system.

Surace aeration is what fish farmers use to carry high biomnass in their brood ponds, but are selddom mentioned on this forum?
G/

Absolutely true George but what Scott is referring to is up here in the winter thick ice and deep snow is what we call the white death. Keeping an area of ice open exposed to air and to allow sunlight in is imperative. It can be overdone, however, in the winter if the pond is mixing the column from deep water vigorously as in a summer set up.

I actually have a smaller compressor that I use in the winter with a diffuser in only about 3 feet of water.

That said, as you allude to diffusers and a compressor are adding very little oxygen to the pond. IMHO their main claim to fame is mixing the water column exposing the deeper water to the open air and nixing stratification. I'm not really sure why it's called aeration either although the exposure of the deeper water does allow atmospheric oxygen to diffuse into the water that is brought up.

I've got a Kasco too and have used it in emergencies in my small production pond in the summer. Even cut a hole in the ice in the winter once in the big pond to open up more water and give a refuge of higher oxygen levels for the fish. Wouldn't think of using diffusers and a compressor to do so if oxygen levels are going downhill regardless of the time of year. In fact, it would probably make it worse once anoxic conditions have commenced.

Hi George, issues I have seen with surface aeration in our northern ponds in the winter are when the power goes down and the ice moves in they can get destroyed quickly.Often running them all winter is not needed or wanted for our warm water types when temps are teens down to zero. (The larger the pond the safer they are for winter use.)Then surface aerators are difficult to remove with thin ice.I think for warmer climates and high biomass situations they are a great tool.I have not experienced a winterkill with properly placed equipment and a good understanding by the pondowner when and when not to run bottom aeration.Perhaps with our colder water holding more DO and lower stocking rates winterkill is not that much of an issue.You mention if conditions worsen you might kick in the bottom diffused and that may make things worse.Consider mixing that water before things get worse,with the surface aeration. If they are in less than 8 ft of water at normal pool ( is full pool rare)look at your disc spacing and see if Todd can repipe the discs as close to each other on the base as possible for more lift.If less than 8 ft have the discs touching each other will give more lift than if there is a spacing between the individual disks on the weight base.Hope you get that 3 ft back soon, take care !!

Thanks Ted, I was off topic talking about hot water and you guys talking cold water. We run bottom diffuser system 24/7 until hot low water.

What I do know that with increased biomass due to drought, my properly engineered bottom system will not prevent a fish kill.
There is no practical way to move those things around is the reason Todd recommended the surface unit - that's all he uses in his brood ponds as far as I know.

Thanks for your help.
George

I am on my way now with a book full of questions. I will post from their place (a new pond boss family!) or when I get back. Thanks for all of the thoughts. I love this site!

Just got back. Their pond is .17 acres. Similar shape to mine, but smaller. The deep end is about 10 feet and the shallower end is 6 feet. They have LMB, HBG, YP and CF. What died was the bigger HBG (8-inches) and LMB (12-14 inches). They saw no catfish or YP dead. They saw about 20 total dead fish for their small pond.

The pond is about 7 years old. The diffusers run 24/7 and are set on the bottom of the two deep areas. They did not know their size, but the looked about the same as mine (Vertex Air One Plus ( two stations with 2 discs each, get one standard and one shallow water model)).

They have not used any chemicals, but added bacteria and used dye this last year to control FA. There are lots of leaves in the pond, but not excessive for this area.

George,

Just curious. Have you ever measured ammonia or nitrites when your water gets low and your fish densities get higher for the quantity of water?

A few years ago I had too many fish in a small holding pond and some yellow perch were piping on the surface just like they were lacking oxygen. But I had plenty of aeration. The water was also very warm. I did a test for ammonia and nitrites and was surprised my nitrites were 4 mg/l! I forget what the ammonia was. My well was down but I got it fixed asap and once it flushed the pond all was well.

After some research I was surprised to find out that the clinical signs of ammonia and nitrites toxicity can mimic hypoxia.

Personally i would not run my diffusers the same place as summer which sounds like what they did. Additionally two diffusers seems excessive to me for a .17 acre pond -- especially in winter -- but that's just my opinion. I'll wait to hear what others say.

Cecil is on target, Even if the stations were large pore discs set in the deepest areas could remove any safe haven of 39F in that small of a pond. Since catfish and YP are still alive its sounds like a thermal issue. I would suggest setting up a winter station in 4 ft of water at one end next time. I would also investigate the pump cfm capacity and the diffuser opeating range to be sure running one station without exhausting excessive air is advised.There may have been other stress at play also and combined with that much heat loss was just too much.Was there a reason from the past that winter aeration was taking place as it can be more difficult in small ponds to keep that delicate balance.

Ted, that's all I run in my pond during the winter is a single diffuser disc set at around 5' deep (depending on water depth). I do exhaust excess air. The open water serves me a dual purpose. Keep the pond open and lets me feed the trout.