Regarding water temperature: The idea range is 65° to 75°. The acceptible range is 35° to 85°.

when water temp is less than 50° or more than 85°, do not feed them. Koi can survive higher temps for short periods, but it is very unhealthy for them. If the temperatures in the pond are consistantly above, do not try to cool the pond by doing large water changes....the rapid change in temp is very bad for them. It is better to shade the pond or to construct a shower filter. For even better cooling, run an electric fan so that the air blowes across the shower filter. this acts just like a mini-cooling tower. You will lose a lot water to evaporation this way, but the water will cool down.

We are getting ready to plant a tree nearby to shade the pond from afternoon sun. Currently it has very little to no shade. I also have several water lilies and water hyacinth that I am hoping will help to shade the water. Have you ever tried "water shade" that colors water blue? I am wondering if it just shades the light that causes algea to grow and does not actually help with keeping water temperature a few degrees cooler. We have a lot of time invested in our beautiful fish and would hate to see them stressed! I definitely was concerned when the water temperature was in the low 90s on Friday afternoon!

I don't think the blue stuff will actually cool the water to a significant degree, and I personally don't like the way it looks. It reminds me of miniature golf course water features! LOL! Water lilies will help though, if the fish will leave them alone. Mine don't....I have some REALLY large koi and they shread whatever plants I try to put in the pond. I ended up installing a couple of shade sails. I got mine from Ebay. The brand name is Coolaroo. they come in blue, green, sand and yellow. It has really made a difference in my water temps!

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Hey, can koi have diarheea? Because something made a MASSIVE dookie in my pond and it was either my koi or my husband...

I live in the North Carolina mountains and currently have a small pond (6'x8') in which i have had koi for 6 years. this pond is recirculating and in winter i put in a small farm heater. The koi have thrived, v\even when the pond surface is frozen.
I am now wanting to put new koi in a new, larger and deeper pond on my farm. This pond is about 10'x20' and is spring-fed, which will always be colder than my recirculating pond. Does anybody have advice on ensuring that the water temp will be ok in this pond? Is the minimum 35 degrees acceptable for extended periods of time?