I've had my betta fish for about a year and half (not sure on his age, as I got him from a lady on Craigslist who "didn't have time" for him.) A few months ago, he was upgraded to a 10 gallon tank with heater, air pump and filter. He has live plants and lives with one zebra snail. He seemed to be looking healthier and acting more energetic than ever.
In the past couple weeks, his aggression seems to have grown. He has started attacking the snail, which isn't a big deal... But my main concern is that I think he's started biting his tail. I used to leave the light on in his tank... When it got to be dark in the evening, he would start seeing his reflection in the glass and would flare up. I'd let him flare a bit and then turn the light off. I've tried keeping the light off so he doesn't see his reflection, but every day there's a little bit more missing from his tail. I'm concerned that something is stressing him out, but there's nothing in his tank that wasn't there before.
Could this be a sign that he's sick? I've also read that as bettas age, they can become more aggressive... If this is the case, is there anything I can do to stop him from biting his tail? Any tips or insights would be great, thanks!