Yeah everyone’s been really helpful, I already have a few tanks and don’t really need another I was just wondering if I could get away with that and have a basically free tank for a bettaIs that jar bigger than most of the betta tanks on the market. Yes. Is is adequate for a betta. Absolutely not. The decision you need to make is do you want good fish-keeper or not? Up to you.
there has been good advice in this thread. Pick up a 20 gallon on sale for $20 get a decent filter some substrate and decorations and provide a decent habitat.
either way make sure you cycle the water before adding the fish.