LoL..I love how strongly pet shop employees advise this guideline! (yet won't tell you to get a heater for a betta * eye roll * )
I bought 8 5lb bags bc they were on sale, and they are like, "WOW what size tank do you have?"
I just lied bc if I said I'm just buying them bc they are on sale & I like to change my gravel color,
they'd tell me to buy more for all my tanks....
They also said I could put a dwarf gourami I was eyeing w/ one of my male bettas in a 5G ... lol