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Koi Babies Low Temp - Shut off filter...Do or Do Not?

14 years ago

Our pond is around 2500 gallons (I think) with 2 waterfalls. This past summer we had small fry like you wouldn't babies. Water is pumped from the lower pond (about 3-1/2 ft deep in center) through the bio filter and into the upper pond (small, prefab 2 ft deep in center). Water spills from the upper pond, over waterfall into the the big pond (5 feet in center), from there over another, smaller waterfall and, back into the lower pond.

My concern is for the baby Koi in the lower pond. In the past, I haven't been concerned because our big Koi could go deeper when the water temp dropped. Our current water temperature is 44°F at the surface. It's supposed to get down to 29°F tonight. When the filter is running, the two waterfalls keep the water stirred up in the lower pond, constantly dumping colder water in. Also, the pump takes the warmer water from the bottom of the lower pond & out to the filter.

Currently, we have the pump shut off. How long can I leave the pump off without risking a lack of oxygen for the fish? I've already found 1 dead, 2-inch koi in the small, upper pond. Do we run the filter or keep it off?

Here is a picture of the pond. (Hate to post it because the pond looks so bad during the winter. I'm dying to get those leaves out but don't want to stress the babies.) Also, a picture of some of my babies.



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