I'm stuck by the computer waiting for a phone call, so I'll just ramble about a subject that I've been thinking about when I'm sitting pondside.
It is a common experience that new koikeepers try to acquire one of each variety, while experienced koikeepers keep gosanke. It is almost universal, however, that without regard to experience level, koi are selected for the merits of the individual fish, and not for the aesthetic effect of the entire collection. A newcomer's pond will usually be a mix of colors, sizes and types. Some sparkle. Some shine. Some colors are bright; some are muted. All such ponds differ, but are very alike in the overall impression, something like a quilt made from random remnants of fabrics with no design or theme. The gosanke pond gives a more dramatic impression, being red, white and black.
At shows, I will see a vat of metallics for sale. The individual fish have marvelous shine and the metallic colors are precious. But, viewed as a whole, the vat will seem dull. How is it that so much shine seems dull? Without the bright reds and black, metallics by themselves give a flat, insipid impression. At one time I thought a pond of a dozen jumbo Yamabuki would be as grand a sight as one could behold. I have since seen photos and video of such at Izumiyu. It was not so grand. The Yamabuki were, but not the pond impression overall.
Japanese visitors have been known to comment on the overall impression of a pond, particularly where Showa and Sanke predominate. The view often expressed is that the pond is too dark, too serious. I recall an article where a Japanese hobbyist urged a western hobbyist to add more Kohaku so the pond would be happy. There is an old Rinko article from back in the 1980s concerning aesthetic pond design, which dealt with selection of boulders and laying of pathways to create a garden that was a miniature microcosm. It suggested that Kohaku should dominate by a 5 to 1 ratio with Showa and Sanke to give an optimistic view and attract beneficent kami spirits.
I have heard people say such things as 'focus on just gosanke and Shiro Utsuri, but add one Chagoi or Yamabuki or Asagi for the visual spice the difference adds'. However, I do not know anyone who actually does this, at least not purposefully and permanently. It may happen that way for a time, but then the koikeeper adds an Ochiba and then a Kujaku. It becomes a mixed pond.
I attended a show several years ago at which one tank of entries grabbed my attention. It held three koi. There was one size 7 Kohaku, one size 4 Kohaku and one size 6 Ai Goromo. All three had intense red pigment very nearly the same in hue, with brilliant white, and the Goromo had gray-blue robing on just the edges of the scales on her back. Against the blue of the show tank, I was mesmerized. I have never seen another show tank in which the entries were so well-selected to compliment one another and impress as an aesthetic whole.
My own pond is mainly gosanke, but six of my 15 koi are not: A Goshiki, a Hariwake, a Chagoi, a Shiro Utsuri, an Ochiba-Goshiki and an Ai Goromo make it a mixed pond. But, the Ochiba-Goshiki looks like a Kohaku. So, I can pretend it is just one-third non-gosanke. I would like to have the overall impression improve through purposeful selection. But, I know that will not occur. My old gals still have long lives ahead and when I add a koi it is because the individual koi grabs me. Still, I think the overall impression would improve if there were more Shiro Utsuri and less of other non-gosanke. Perhaps over the years ahead I'll shift the population in that direction. Perhaps not.