| I don't think I've ever seen a scientific documented sheet on what your asking.
I do know that if kept indoors without speciallty bulbs to replace the natural sunlight, the koi's color and skin suffers. It is particularly noticeable in young koi, who can be easily
damaged in their ability to fully develop their color.
Those closet to the equator have to deal with extremes of sun and most outdoor ponds have to have sun shade provided or they can actually get burnt with our cystal clear water......
There is a reason why so many japanese breeders are building greenhouses to emitt more light as their koi are held during the winter |