Your betta fish bites you because:
- It’s curious
- It’s defensive
- You were mistaken for something else
Your betta might become curious why your hand is inside his tank. Because your betta doesn’t have hands, it’ll use its mouth to find out what’s going on. Your hand might also make your betta feel afraid or threatened, causing it to bite out of self-defense. Lastly, if you use your finger to feed your betta, it might just get carried away and accidentally bite you.
Generally, you shouldn’t stick your hand inside your betta’s tank unless you have to. Aside from spooking your betta and getting your hand bitten, you might accidentally introduce harmful bacteria into the tank.