On the flip side I have encountered an employee in a big box store who cared a little too much about the fish. I was trying to buy 10 neon's to put in my 29G, even after explaining to them that the tank was cycled, that I have multiple tanks, that the tank has a filter rated for a much larger tank, that the only other fish are 2 BN pleco's etc they still refused to sell me the neons that I wanted.
I could understand where the employee was coming from, and was happy to encounter someone who knew what they were talking about and cared, but it was incredibly frustrating being told I could not buy 10 neon's.