So many girls...

It's common in many marine species, actually.

http://www.nytimes.com/1984/12/04/science/sex-change-in-fish-found-common.html

http://www.bio.davidson.edu/Courses/anphys/1999/Rice/Rice.htm

reef fish..yes salt fish ok sure...but we are talking guppies on this thread..and your post made it seem like almost all fish do it..when it is pretty rare in freshwater.

of it were true than many pure guppy strains would be ruined by a random female turning male..witch after speaking to many people about line breeding and the such i have never heard of happeining

No...I never said that guppies changed, just that sex determination in fish is not a simple matter set at birth, like it is in mammals. If an entire brood of trout can be made functionally male by adding hormones to the water when they're fry, freshwater gender determination is obviously more plastic than it is in mammals.

so off topic ..ok