Here are my 1 gallon bowls that I had my 3 Bettas in while I was staying at my moms house years ago while recovering from cancer surgery and a bad divorce...
People told me in nice and not so nice ways that they needed heaters and filters and all that. (I did add plants a little later after this photo was taken) I was so happy just to have them with me and be good for my recovery and something to keep my mind off of my pains. But some ppl made me feel so bad that I was doing it all wrong. But I did change the water every day in all 3 bowls, it was my therapy for after surgery rehab to get my body moving again, doing something.
These 3 Bettas are the only ones that I have ever owned that lived for many years. I've had Bettas in 5 gallon tanks, 10 Gallon tanks, and a 30 gallon tank and so many end up dead at such a young age for unknown reasons. My "Bowl Bettas" were the most healthy and lived the longest. Starange I know, but true for me in my case.
Left side: Gary, Middle: Kitty, Right side: Greg
This is Chester in the next picture in his 1 gallon tank. Soon though he will be in his new LED 5 gallon tank. It is not done with it's cycle yet like I hoped it would be.