Do males get them too? Because my male betta gets a stripe down his body whenever I take him out of his bowl to change the water, and then it disappears in an hour and I don't know if that's normal.
not to hijack, but is it possible that they have striped coloring like that? my one girl (cade) has always had stripes since i got her, but she doesn't act stressed at all. she acts very happy in her current tank, swimming laps and chasing my finger around, no clamping or hiding.