I just moved my Betta tank, so the reflections are different than before and he's adjusting. My tank is a standard 10 gal with stock lighting, black gravel, various rocks, silk plants, and java moss, and a background just on the back side. The problem is the ambient light from the window is creating a strong reflection in one corner of the tank, and he wasn't used to it.
I ended up rearranging to put a tall plant in that part to block the light somewhat -- he still does it occasionally, but not to where he's stressing himself out any more
