In the hobby or in industry?
There are many people in the hobby who do exchange eggs and make sure that
their stock comes from known strains. But how many people are members of
(inter)national rainbowfish groups?
As far as industry goes, they are out to make money. I would be surprised if
the majority of people in the industry are as diligent about keeping strains
pure as serious hobbiests. Most pet store customers don't know enough to
demand quality fish, and most pet store staff, well...
I'd recommend joining a club like NANFA in Australia or the RSG in the US
and getting some high quality mops or fish.
-- Stephen
Grayslake, IL USA