Can we keep bettas in bottles and jars with out a heater with air bubbles ???

How often do you plan on doing water changes?

How warm will the water stay in the room you're keeping the fish?

Not sure, thats what I want to know.Resembly sunny in the mornings.

A jar, in direct sunlight will get FAR to hot for a betta.

As the heat rises, there is less oxygen in the water.

The temperature will change a lot each day and with each WC.

Not only that, but they barely have enough room.

I would not do it.

Because they are tropical fish they need warm water. If you lived in Tailand you could keep them without heaters or if you had a room that stayed at a constant warm temp but if not, then NZ is a cold place for a fighter to live

I have mine in separate containers from Plastic box and just have lots of containers in one big tank. This way I only need one heater but i do water changes in their containers ever 2-3 days.

A jar, in direct sunlight will get FAR to hot for a betta.

As the heat rises, there is less oxygen in the water.

.

Betta breath from the surface anyway :lol:

A large jar will be fine provided the temperature is constant (25 deg ideal) without too much fluctuation and water quality is premium (daily waterchange or at least every second day).