My betta has been biting his tail
I noticed that my betta had a rip in his tail about two days ago. It didn't seem to have any black or white rotted looking areas on it. Now it looks like he had torn his tail more so its half the length it was. None of his other fins are falling apart or have any clamping, strange coloring or rips. It's just his tail.
I saw him earlier spinning in circles looking like he's trying to chase his tail. I exercise him every day by putting a mirror in his water for a few minutes so he can flare at it, or stick my finger in the water and am in my room a good amount of the day lately, so I don't think he's bored. I don't know why he's suddenly started this habit. I'm hoping the water change will help, perhaps he was stressed, or it might have been the plastic plant-the plant has leaves fairly rounded but perhaps they were sharp enough to tear fins. So I replaced it with silk plants with no sharp edges.
Any idea why he might have started this? He's a healthy fish, is very active, has a variety of foods and eats them well, I keep his water clean, keep him entertained...but he's biting his tail apparently (since there seem to be no other sign of disease and his circling behavior i'm assuming he's nipping it)