I have not once heard of feeding goldfish to a BP... I mean, I guess it couldn't HURT, but I'm pretty sure they need the quality of red meats to sustain, so maybe the goldfish were an occasional treat? I don't think I'd personally try it, with how picky BPs can be. If a snake likes the taste of a fish, it may not want to go back to rodents, which could pose a supplemental issue.