About 6 mos., except for stinky & feisty. Stinky lived for over two years and came down with something I couldn’t identify. Feisty sadly passed because I was messing with his tank and accidentally released a nitrogen bubble. That was the last time I kept one in a “traditional” betta tank. I really hate those things. They’re so cute and small and fit just about anywhere. Which is bad for a fish tank.
Yeah, the tanks that are made especially for betta fish are not actually big enough to put any living thing in, besides maybe plants and a few snails. I hate that those tanks are sold all over the place.