In response to the gender thing... I find it much more difficult at work to convince the OLDER generation (60+) to do things the "proper" way than the new generation.
I had an older gentleman in who only had a 40 gallon. He bought an oscar and two convicts to go in there despite my explaining to him that it wasnt enough space.
I had an older woman who had 4 fancy goldfish in a 10 gallon tank, and wanted to add a 5. I told her it wasnt a good idea, but never refused to sell her a fish (technically i cant where i work) and she went to my manager and complained.
I've had more rude comments that I am a "dumb teenager" from the older generation... Not that there is anything wrong with being a teenager, but I'm almost 24 and find that insulting. I also have a degree in Animal Science, have had tanks most of my life, etc.
On the other had... I had a younger couple in the other night and our competitor had basically told them get a ten gallon, throw some fish in, youll be set. All their fish died within two weeks and they wanted to start fresh. I got them a heater, a gravel vaccuum, a API masterkit, and went through the process of cycling. They came back a few days later after a water change (i told them not to touch the filter) and talked about their test results... They decided they are going to do a guppy/snail/ghost shrimp tank.
Another younger woman bought two ADF's at hallmark.... I talked to her about how bad of an environment that little 1/4 gallon tank was and she upgraded t0 a five gallon... with a mini heater! Now the frogs are alot healthier and are actually swimming around and eating!