Sure, you do not need a heater if you live in hot places like Florida. (Might not be that "hot", but hey I am in Michigan lol).
Betta are in fact playful fish.
The reasons for them being inactive could be
1. There is not enough room swimming room.
2. The water temperature is too cold.
If they have an at least 5-gallon tank with ideal water temperature and everything else, they will be very active. Haven't you heard? Betta fish are dogs in a fish's body?
I wouldn't worry too much about the bubbles. I see them all the time on the same day after I have done a partial water change. Sure, there can be a lot of reasons for the forming of bubbles inside the fish tank. As long as the fish act normal, and all the readings are fine, then there is nothing to be worried about.
Would you mind share some photos of your betta tank?
