The good Corrado, known especially for online Invertebrati.INFO , made ​​me reflect on the use of the terms "variety" and "race" for the various selections of crosses of the same species of fish.
And then I went to look for some useful definition to understand why, in aquariology, use the term more often VARIETY 'to define a particular selections, for example, A. ramirezi , or Guppy .

In animal husbandry, infati, r Azze the animals are "types of individuals obtained by artificial selection, whose characters are transmitted by inheritance to the descendants." So we use the term RACE for dogs or cows ... and what a blond or a ramirezi fullred Guppy , if not exactly artificial selection? In the sense that he was the man to put pieces around repeatedly with certain characteristics to ensure that their offspring presented these features with greater frequency or intensity.

The variety should instead identify only "groups" of individuals with similar characteristics that have ... but for natural reasons, not as a result of crossovers dictated by man. So if I dive into a lake and I fish the same species in an area all have longer fins and are instead part of a shorter, these 2 groups potri say that they belong to "variety" several of the same species.