I’ll bet they don’t live in a light bulb. These certainly do and they seem pretty happy about it. This would be a great idea for Bettas better knows as Siamese Fighting Fish. Bettas do not get along with others very well and unless they are looking for a mate they don’t even like each other. Because these fish get their air by swimming to the top of the water to get little snippets of air, this would be a perfect home for them.
As a note, be very careful to wash the inside of the bulb with extreme care as any frosting, glass or other tiny matter left in the bulb could essentially be a death sentence for your fish.
I would love to see your mini-aquariums so please send pictures and other ideas.