Read something, can't remember where, about fish farms in Asia pumping dwarf gouramies in particular full of hormones or something to try and produce more male characteristics - even in the females, since the males are the more commercially valuable. Sorry I can't recall more of the details.
I had bought a dozen or so blue neon dwarfs 'cuz I wanted to try to breed them but have never had much luck even keeping the imported females alive and finally just gave up. Couldn't find anybody that raised them domestically either, even through these forums.