These guys seem to be the real deal - everything they've told me has checked out when I've looked it up on the web, and they have some excellent display tanks in the shop. There's two shops like that in my city - both specialist aquatic shops. Talking to them, you can tell they are knowledgeable and passionate about aquaculture.
I've had the experience you describe, but at the pet stores that sell a bit of everything. One of them sold me a pleco when I only had an 85 L tank. I should have researched it myself, but still...