Just hormones in response to changes in atmospheric pressure, triggers lots of fish and inverts to breed. Ideally its good to have a patterned or photographic background with bettas so that can't see their own reflection too clearly. They are unfortunately dumb enough to attack their own reflections. Cute little fish, but brain surgeons they arent.lol. Limited IQ and raging hormones, bound to cause problems.Lol.
I think that his tank glass has some sort of mirror effect going on as when i put a black and A patterned background he went even crazyer for his own reflection so that came off and now i have just let the algae build up at the back (the snails keep it in check but not enough to be clear) this helpes a bit
If you can't fix it with a hammer, you've got an electrical problem.
You can just WC melafix out, when it degrades its not toxic or a massive food chain toxin like dyes and formalins can be. It will eventually decompose perhaps pushing nitrate up a little but with sensible water changes you'll never notice.