New user here, but no stranger to internet forums. I have gotten many of my questions answered here before via searching, but the questions I have now I am looking for more specifics based on my construction, as all ponds, climates, etc are all different.

I build a small ornamental/goldfish pond back in May this year. Has approx 800-1000sq ft surface area, and approx 15000 gallons.

Look at the first 3 pics to see.





Some background. This is my second koi/goldfish pond. My first one at my old house was around 3000 gallons, and about 3.5-4' deep and had a 1200gph pump that sat on the bottom, tee'd off for a waterfall feature and a fountain both. First winter I shut off the waterfall and left just the fountain running (I like the sound), and this resulted in a total fish kill. Circulating TOO much water off the bottom and not allowing that water to stay 38-40 degrees. I super-cooled all the water and the fish cannot survive in 32-34 degree water. At least this is what I was told. Going forward I only circulated just enough water to keep an opening in the ice. And those fish lived a happy 5 years before I moved.

So here we are at my current pond, 5x bigger. And currently have about 50 goldfish in there that are ~3-4" long.

Would it be acceptable to leave the pump run. All it does is feed the waterfall, no fountain. And more importantly, it is on a shelf at 2' depth. Below the shelf, the pond has a flat bottom approx 5' deep, 4' wide, and about 30' in length. So a good 3000 gallons of water BELOW where the pump draws. And the pump/waterfall are all at one end. And its a 3600gph pump.

In the last picture, you can see the construction of the pond. And the shelf on the left is the shelf that the pump sits on. Its in the bottom in the pic cause I was just testing the pump.



So....what would you guys do? Leave it run drawing water from the ~2' level at 3600gph? or would you remove pump and put a de-icer in which I am hoping I dont have to. But if so, what would you recommend.

And sorta related, at what point of pond size is keeping a hole in the Ice no longer a requirement? I live in central ohio. And while the last two winters have been mild, the "norm" is for a pond to freeze over for a month or so straight, and Ice 8-10" thick. Hundreds of farm ponds in my area that are great fishing holes, and freeze over with no worries at all?

First of all welcome.

Our pond is much bigger but we run our fill pump all winter long in over our waterfall. It is a 5500 gallon per hour pump with a 2" line. It runs all year long with no foot valve.

Our water is ground water field tile run off, and its warmer than freezing. I personally would be worried about super cooling all your water if you let it run all winter. I expect it wont freeze but keeping the water moving and circulating maybe too much.

We have had over 30"s of good solid ice on our pond but still running the water fall from our fill pump. The extra water runs out the over flow and the front of the waterfall gets a solid ice layer but the water is flowing behind it.

One tip my poker buddy has a koi pond and went to Mexico for a holiday. He came home to find the pond frozen over. In a panic he grabbed a sledge hammer and broke a hole in the ice. Next spring that hammer shock killed all his koi every one of them.

If you don't have a bunch of organics built up in the bottom of the pond yet you should not need to worry to much about keeping the ice open to let the gasses out.

Cheers Don.

Even with the pump drawing water from a depth of only 2', and the flat bottom at ~5.5' down, you still think its too much circulation and that the bottom water will be impacted.

And there is actually quite a bit of organics built up already. Maybe a good 1" layer. The pond is sandwiched between a ~14" diameter maple tree and a ~20" diameter pin oak. And I think every single leaf that falls off one of them trees eventually make it into the pond.

And regarding climate for those unfamiliar with central oh....

I'd say on average we would get a 4-5" ice layer over the farm ponds in the area. (I have a 1 acre farm pond out back, ~8' deep and 60 years old). On the hard cold winters, I have seen ice 10"-12" thick. And then I have seen winters (the last two) where the pond never froze completely over

I would think this is something you can easily test now. With the pump running, check the surface temp and the temp on the bottom. If they are the pretty much the same, you know the bottom water is being circulated by the pump.

I'd do the water temp test like Bill D suggested, but my seat of the pants thoughts are that you should put in a de-icer like they use for a stock tank. In ponds, ideally you want 5%-10% of the surface to be open to the air, to degas but more importantly to have the water pick up O2 from the air and a to let sunlight into the pond so the phytoplankton can produce O2.

As to how large a pond has to be to NOT require open water, it's more of a question about how large the BOD is on the pond.

List of acronyms

Oh and a big welcome to the forum!!

What about a submerged light or two on that shelf? Perhaps one with a grow light bulb. Some heat, some light......it might even be pleasing to the eye.