At a store I used to work at the actually implemented a buy the pleco, grow it up and trade it for a younger one....try as I might I couldn't convince people to get smaller algae eaters (do they even know that not all "plecos" eat just algae...or any at all??)
It was fustrating or me telling them about id sharks etc and rtcs and tsns
Me: "These guys get huge fast, so unless you're willing to commit to a pond for this litter guy, I'd suggest something else if you really want a catfish" (walks over to corydora section)
Customer: "well, that takes forever and they only grow to the size of the tank, so I want one. Besides, I've had 15 of these guys in 10 years, and they all lived for a year or so"
Me: "Actually, that's not entirely true. Even though fish kept in aquariums don't generally grow as large as they would in the wild, they still get big. It'd be like taking a great dane and putting it in a kennel ment for a small dog. The dog will die because of inadequate conditions"
Customer: "No, that's not true, I want to talk to your manager"
Me: "That'd be me"
Customer: Oh...(turns around and leaves)