I think that both Helene and Bill Little are right. Helene in principle and Bill in practice. The method proposed might work with the lesser “problematic” Paro-species (as there are linkei, filamentosus, quindecim or paludicola, maybe nagyi too) but probably not with the others. The species named are more adaptable than others, if the changes occur slightly and slowly. It’s no serious problem with the adult fish, it’s a problem with the eggs and the young larvae.
Therefore, I should prefer a different method and choose this one in case of quite a many self-produced offspring of the named species only. This would be my strategy: to produce many young with a somewhat more complicated method, and then – perhaps – make some experiments.