| Mike:Average water temp. of an outdoor shaded pond in M'sia is about 29C, Ph 7 to 8,water hardness somewhere between Japan and UK ( on basis of hotel shower experiences -soap lathers and skin feels ! )
Generally,the shiro utsuri has highest success rate ie they actually improve in overall apperance,with more and better sumi over time,after they are brought in from Japan. In comparison,its much harder trying to maintain hi quality in gosanki; the hi colour and lustre tend to fade somewhat over time and the quality of the shiroshi or whiteness also tend to deterioriate.Keepers who can afford chillers ( bringing water temp down to between 20C-24C ) are able to maintain better quality hi and shiroshi,so I guess temp is a greater contributing factor than ph and water hardness in M'sia. The other significant factor is growth rate; for the good bloodlines,especially those which have been backbreeded with magoi,the growth rate averages about 1cm per week when they are between 25cm to 55cm ! The hotter temp makes them more active,eat more and grow fast! Hence,the hi has a tendency to get lighter unless the percentage of spirulina feed is increased.Once they stop growing,the hi does gradually gets deeper in colour again. In the rapid growth stage,maintaining good shiroshi whilst subject to high temp and spirulina,is a real challenge!
As for showas, the hi found in the hi-showa (which seem dfferent from the hi in kokaku and sanke ) variety do tend to sustain better;but I don't personally prefer this variant of hi to the hi type of the better known kohaku and sanke bloodlines.Hope the way I describe it makes sense !
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