I don't know 100% about sexing sparkling gouramis (for others it is:), the dorsal fin of the male is long and pointy and the dorsal fin of the female is shorter and round. It's hard to tell when they are young. I agree that you should ask the LFS employee how you tell. Due to turn over and what not LFS can be spotty about their knowledge. If they tell you any other way, then they don't know what they are talking about. Also, I would watch the tank for a couple of minutes and see which fish cling (for lack of a better word) to one another. If they stick together and they aren't nipping eachother, I would go ahead and get that "pair".