Betta fish and stress-related diseases

[dalexion]

I'd also check for reflections. My betta was glass surfing like crazy until I covered the back and sides with black paper. Now he's way more chill.

[Hammer]

How old is your fish? Older bettas tend to slow down a bit, might not be stress at all.

[Vitalix]

Ever tried adding Indian almond leaves? The tannins can help reduce stress and mimic their natural habitat. Worked wonders for my guy.