I still think it is mostly genetics regarding color. Unless of course
you have access to one of the ponds in Nigata province in Japan in
which to overwinter your fish(and hope it will be found and returned to
you in the spring.) Good water is always important to clear colors, but
nothing guarantees it. I have what was supposed to have been a
Dianichi kohaku, that lost all of its color, and is very small for it's
age. We do have some 26" koi, so it's not pond size alone. This guy is
only about 12", and is the same age or younger than some of the big
ones, aprox 8 - 9 years old. I give up, I just enjoy them and accept
what we get!!
Olde Hippee