| Mike, that article is twenty years old. And it was an observation based on a few show fish of the day- utsurimono , shiros and showas are a very different animal than those born in 1982?
Having been to Taiwan and having seen many hobbyist ponds and dealer/breeder facilities, I can tell you, that the fish grow well but high class fish don't hold quality color very well. The locally produced fish look better than the imports. And most of the imports there when I was going there were from Southern Japan- Hiroshima. The big competitors import ' fresh' fish each year.
The reference is Isawa is way off as the well water in winter is still cold ( 59F). The koi are brought indoors in Isawa just like in Niigata.
Here is the pH and saturation level at indoor temperature of 59 F in Hiroshima in winter ponds- |