Bettas need a minimum of 2.5 gallons of tank water (5 gallons is recommended). Big chain pet stores like Petco and Petsmart are selling tanks under 2.5 gallons marketing towards betta fish. Not every betta owner does their research and picks the smallest thing the big chain pet stores sells. Now although the owner still could of done more research Petco and Petsmart still are putting betta fish on the boxes of these tanks. If you do not believe me here are links to tanks who either tanks that have a picture of bettas in the tanks or says can fit 1 betta in the tank. 

1. https://www.petsmart.com/fish/tanks-aquariums-and-nets/aquariums/top-fin-slosh-deep-sea-creature-aquarium-42622.html?cgid=300129
2. https://www.petsmart.com/fish/starter-kits/top-fin-excite-aquarium---1-gallon-
3. https://www.petco.com/shop/en/petcostore/product/imagitarium-betta-fish-dual-habitat-tank-in-blue
4. https://www.petco.com/shop/en/petcostore/product/imagitarium-betta-desktop-kit

************************************DO NOT BUY!!!*****************************************

I even picked the Top Fin brand which is Petsmarts brand and Imagitarium brand which it Petcos brand. I feel big chain pet stores should be selling the right size tank tank, so I encourage you to sign the petition to get rid of tanks under 2.5 marketing towards bettas i feel selling that and marketing like that is betta abuse.