regarding Hasegawa,
and the yellow heads mentioned, please check the video or dvd and then report back, otherwise your comments add nothing to the topic and are rather ignorant.
"a bowl of males"

= check the video

.
as for yellow heads being nothing, i dont agree.
as far as im concerned a koi with a yellow head is pretty ugly, sure it can look nice if perfect in all other areas but to me it does not make the grade.
kohaku are meant to be red and white, not red white and yellow!
as far as koi changing from a yellow head to a white head over time, yes this can happen, but it is not a certain bet, more like 50/50.
choose a koi whith the whitest head to start with, if you wish to have better odds. unless off course you like yellow heads
kevan.