I got on my pond to ice fish it for the first time yesterday and noticed something was seriously wrong. In the few clear spots I could see through the ice, I saw dead or dying fish. I punched a bunch more holes and noticed really small fish hanging out by them.

Today I broke out the oxygen test kit. It was terrible.


Grabbed a trash pump and my back hoe. Broke a bunch of ice with the hoe.


Cut some holes with my auger and got the trash pump working. It started melting the ice faster than expected. I figure at this point, the more water I can expose to air, the better.


I had a pretty good hole by the time I had to quit.


Background. Old pond. Had a partial winter kill last year, but had a long, heavy snow winter. This year has been mild, some of the ice still isn’t safe. Had water running into the pond off the hay meadows on the warm days. Still water coming out, so I didn’t think I had anything to worry about this year. I was wrong.

Questions. Is there anything else I can be doing? Should I focus my pump aeration efforts in one area, or move it around? Should it be in shallow or deep water?

Thanks for any advice. I’m going to get an aerator installed before next winter, but I had to pay for my daughter’s wedding this year, so funding was a little short.

Suck from the shallow water and spray as much as possible up in the air to get as much of the water as possible in contact with the air. Pushing the exit water as far away as possible from the intake is a good thing.

The cloudy ice is what bit your pond in the butt. 2" white ice, 2" snow is all that's needed to stop sunlight from getting to the phytoplankton and plants to allow them to make O2, so they consume O2 along with the fish. I've seen winterkill happen in as little as 2 weeks.

The more area of the water that is exposed to the air the better. Do another O2 test tomorrow to see how much it's changed. Ideally for winter aeration you want about 10% of the surface of the pond to be ice free.

If you can leave the pump running all night long that will help.

The gas tank on the pump lasts about 4 hours, so I can’t risk it freezing at night. I will restart it first thing in the morning.

Have you thought about solar aeration? Doesnt work every day but mine seems to grab enough sun to keep an area open almost 24/7

Your ice this winter looks not too bad at all compared to "normal" Colorado ice and snow. I would expect you have had worse several times over the last decade?

You say this is your second winter in a row with a fish kill. Any chance your pond has been at maximum carrying capacity of fish for the last two years? Have you been culling significant fish from your population based on what your sampling is showing?

You may have a lot of oxygen consumers below the surface.

Hopefully, after your rescue efforts, will you will still have a lot. However, you may need to evaluate your pond population this spring.

To follow up, I spent about a month pumping water into the air and opening up large areas of the pond every day. I was seeing a few live fish for the first few days, so I was hopeful. I kept it up until it wasn’t safe to go out on the ice.

As the ice thinned, I started seeing dead fish. Lots of dead fish. Big and small. As the ice got thin,the eagles figured out they could pull them out of the ice. It was pretty easy living for an eagle this spring.

There are 5 bald eagles in this picture.

Now that everything has thawed out and starting warming up, I’m pretty sure I’m looking at a total loss. I have not even seen a crawdad.

So what happened?
There are still millions of zooplankton in the water. I see them moving almost everywhere I look.
There are more cattails in the water than ever before. Weed growth wasn’t much different than years past. Maybe the water coming in carried some nutrients that the zooplankton liked and they blew up and used all the oxygen? Maybe too many fish? I have been culling some bass, and as I lost a lot of the larger ones the year before, I thought I was ok as far as numbers.

Any ideas are welcome. This pond is close enough to power I’m going to go with traditional aeration

Sorry, my heart breaks for you. I'm leaning towards , needing more culling, possibly combined with to much cloudy Ice. A reminder that I need to heavily cull this summer/autumn. God bless you and yours.

These two rules apply to just about every fish kill:
1. There are more fish dead than what you can see
2. There are more fish left alive than you believe

Sorry Brad!

Theo's two rules definitely apply. Create a rough estimate of the species, size, and numbers of your dead fish. Some of the experts on the forum can then tell you if the kill was perhaps due to too many fish above the carrying capacity.

Adding aeration in the future can certainly increase your winter carrying capacity. (And your hottest part of summer capacity.)

Also, remember his Rule #2. Hopefully, you have a significant number of your smaller fish still surviving. Keep sampling your pond this spring and try to determine what you have left, and what you may need to add to have a nice fishing pond again in the not so distant future.

Good luck!

Rule #1 is obvious, rule #2 tho is a big plus, and remember, just a few fish from different species can populate a pond pretty fast if the predator count is reduced like it is.

We had a similar event with otters just cleaning out a pond, what we thought was just about completely, We are just starting to get a some pretty good fishing again, re-homing a bunch of otters in the meantime, but they have reproduced and I'm thinking the new offspring are more wise to otters because they were raised around them from day one, unlike the original fish were used to beavers amongst them all the time so they had no fear of them.

I really can’t get an idea of how many fish died, because the eagles ate them before all the ice was gone. I know it was enough to feed 5 eagles and a bunch of ravens for 2 weeks.

I hope I’m wrong that they are all dead, but the herons and mergansers don’t think there are any fish left, either. They are all hitting my other ponds, where I am seeing a lot of fish.

Where it is sad that a bunch of fish have died, starting over will take time, but will be an interesting journey.

The more organic matter there is in a pond, the more bacteria is in there to decompose the organics and the bacteria chew up a bunch of O2.

As for aeration. Grid based, shallow water for winter, deep water for summer if the water is deeper than 10'. If you want help designing a system we do that and also sell them. We sent a lot of supplies out to a pond owner near Montrose, Co.

Who is your customer in Montrose. First name is enough.

Chad, but the property was sold. it was a 10 acre pond. Absentee landowner, lived in another state.

Do you know a Mark Rackay? I've been hunting with him a few times out there. For the life of me I can't remember the name of the outfitter. The outfitter is in a wheelchair and if memory is correct he also owns or owned one of the pawn shops there in town.

I don’t know Mark. I do know of the outfitter. He used to lease the ranch next door to us. Beer cans on the road, gates left open, trespassing. The game warden talked my neighbor out of leasing to him. Please be careful. Just because you are with an outfitter doesn’t make you immune from prosecution. As an outfitter, he has a very poor reputation locally.

I checked out your web site. I will send you an email when I have a little more time. We are high enough that I don’t normally have oxygen issues in the summer. It is likely to be fall, when I sell my calves, before I can put the money together for this aeration system.

Brad, thanks. I haven't been out there for a few years, and if I go out there it will be with a different outfitter. We didn't have any of those issues when I was there, I think it all depends on the guides that he hires since he can't be out in the field personally.

Give me a shout this Fall and we can get something figured out aeration wise. Even if it's a DIY system, we have parts/pieces too.