Not every store is perfect in their identification of aquarium livestock. Expanding on that, bit every wholesaler is perfect either. Because of this, there are numerous species that go misidentified every day. On one hand, this could benefit you, the consumer, as you might get a fish that is rarer than the one you thought you were buying. On the other, that statement could easily be reversed, and on top the that, the misidentified fish could have a whole slew of special requirements that you are unaware of. This predicament could be avoided if you researched your fish thoroughly and avoided impulse purchases. Basically, you need to become an expert for the fish you want to own, and stick to that list. And even the there is no 100% guarantee that you are getting what you paid for.