It's really not "OK". The highest temperature Koi will stay healthy at is lower than the lowest temperature most of the other fish you have will stay healthy at, unless you really don't care if you shorten the life of your fish or make them susceptible to continuous illness. I guess if you shorten the Koi's life it will eliminate the future problems you'll have with a fish that can get 3 feet long while also being massive.
aquaticdelights.com
goldfish and koi are from different lines of carp... goldfish were from the common carp whereas koi are from amur carp which are naturally found in southeast asia=tropicalThe most common cold-water fish species is the goldfish, followed closely by its larger counterpart, the koi.Cold Water Fish Species for Your Freshwater Aquarium
Optimal water temperature is vital for a community fish tank. Here are some cold-loving fish that will flourish in your cold freshwater aquarium.www.thesprucepets.com
Even though koi can survive in extremely cold or very hot water, it does not mean that they do well at these temperatures. This is especially true if the extreme temperatures persist for long periods of time. Koi tend to do well when their water is around 65 degrees or slightly higher.At What Temperature Should You Keep Your Koi Fish Tank?
As a koi owner, it is crucial that you keep your koi's tank or pond at a reasonable temperature. Koi rely on the water temperature to assist with their digestive process and cannot digest food if the water gets too cold. Failure to keep your koi's water within the acceptable temperature range...animals.mom.me
Coldwater fish in terms of the aquarium trade refers to any fish species that prefer cooler water temperatures. The optimal temperatures for these fish hover around the 68-degree mark, although each species’ temperature range may vary from the norm. The main take away message is that cold water fish like cooler waters compared to their tropical fish counterparts. Typically, these fish can survive at even lower temperatures for a period of time. The most notable fish species that you will see in chain stores that fit this category would be Koi, Goldfish, Zebra danios etc.What's The Difference Between Coldwater Fish and Tropical Fish?
Newbies just entering the hobby might get confused about whether to set-up a cold water fish tank or a tropical fish tank for their first tank. While both tanks are relatively easy to set up and maintain with proper knowledge and care, there are some fundamental differences that need to be...
I could go on and on and on with sources. You are simply wrong and giving very bad advice.
