In japan among the breeders own ponds there are some that annually favor growth, some that favor beni, some that favor sumi....and the apprpriate needs of the koi are met by the farmers.Toshio sakai (my hero ) takes many of his tategoi from Isawa ( a hot springs area where the colors are livid ) and transports them up to niigata to give them something different from the mud there.
kentaro sakai of Sakai fish farms is a friend of mine and has entertained me with stories of rain storms full of manufacturing drift that dramatically change
the PH of growth ponds. Awaken in the wee hrs of the morning by a PH dropping alarm, they spend their sleep time adjusting PH on the run, then without sleep put in another full day with regular activities.
here in washington state we have plenty of snow melt run off available. many of our cities draw from that to quench the population's thurst. It's very soft. On low snow years they use ground water from wells and boy can I tell by the pond's water #'s when they do that. Used to drive me cracy...till I went to RO (reverse osmosis) water.
While this rambling doesn't answer you question direct,I hope it does give you a feel for some true life experinces.....
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