With your najas grass/java moss you could even support single bettas in those jars with little problem. They might be a bit hard to see and appreciate though.
Really? The jars aren't even half a gallon, I do know a breeder in my area that does have there bettas in those jars. Would the jars work long term, or short term?. What would the water changing schedule be?
The water changes would be close to 100% daily. You basically start with fresh water each day. They work for quite a while. Your breeder acquainatce is probably keeping all of his stock in their own jars until they are large enough to sell, which would be several months old and full sized fish.
Yes. She is named Bettascapes on Aquabid, I would highly recommend her. I believe that she does have quite a few "personal fish" that she keeps long term. They are in larger tanks. Thank you. So around 3 months would be okay. That's how old my fully grown Mae was when I bought him