Ok, to add to the original part of this post, basically every "tank" that Petco has under the bettas is horrible! They are either really small, or both really small and divided for 2 bettas. I mean, the betta can hardly turn around in those things! When I got my new girl betta there was a woman there looking through the bettas (and being quite rough as well). So she starts looking at those tiny little tanks at the bottom too...I then knew that she obviously didn't know anything about bettas. So I educated her :) Actually, she ended up talking to my mom and I heard some of the conversation so I came over. She asked about breeding bettas so I explained it (and how it should only be attempted by someone knowledgeable). I won't bore you with the entire conversation, but I also managed to interject in a nice way that bettas need a heater and that I keep mine in larger tanks because they do need space to swim. I did this after explaining the breeding process so she knew I wasn't just some "stupid teenager". I don't know if she will do anything, but at least I knew I tried.
Honestly, I wish I could just smash all those little tanks under the bettas and replace them with larger tanks with heaters labeled "betta tanks"! Then maybe people would just blindly follow that new trend too!