Yes, I think that’s something I have learned now, too ……….. I will never again buy fish from a store, at least if I am not convinced to get both sexes. And I have learned how “easy” the determination of sexes is 😉
But something I would really appreciate – that this should be told in the many advices you get about how to determine the sexes of paros: that the possibility of having dominant females which appear to be males is always given, at least in some forms/ species. If you read about sexual determination of paros, it always seems relatively easy to do: males have coloured unpaired fins, female never have. If you can’t see it clearly (for example because the fish are ancious in the tank of a fish store) – then take a torch with you, and you will see the colouration of the males.
And really – this is not right, not as a general rule. There should be hints that something like what I experienced can always happen – that females seem to be males, at least in non-expert’s eyes……