So in this case the person would have to go to the shop, take a picture of the fish, then go home and somehow work out that what the shop sells is in fact not a Flying Fox but a Siamese Algae Eater?
I'm saying that when the shop is confident of what they have, they should sell it as that and not some pseudo made up common name like "Black Line Flying Fox". Have you googled that name btw? it will certainly lead you in the wrong direction of which fish it really is.