Help! Fin Rot Vs Fin Damage

HI all! I have a curious and active betta named Watson, who has either fin rot or fin damage!
He was in a smaller tank initially and I assumed he got fin rot on his back fin when I let the water go a little. That was several weeks ago. Still learning. Anyway, he's been upgraded to a 3 gallonwith frequent water changes and his back fin did not seem to get any worse. Just now I was watching him goof off and realized his analfin was torn (could have sworn it was fine earlier today). He has a filter in his new set up and has been enjoying playing and exploring around it, as well as surfing the current. He also has a vase tank decoration he likes to swim in. He is very exploratory and active! So, from the pictures- is it fin rot or damage? Thanks!!!!

 

Do you think it's that vase below? I have one just like that and it was very sharp and I had to sand it down. I suggest taking that out and treating a quarantine tank with melafix. Good luck!!

 

some people say melfix is bad for bettas. but I didn't know that until I added the average dose to my tank. I think its fine in small doeses. just my betta reacted normal.

 

some people say melfix is bad for bettas. but I didn't know that until I added the average dose to my tank. I think its fine in small doeses. just my betta reacted normal.

Mhm never tried it but it worked wonders on my fancy goldfish

 

This looks like damage to me. And by damage I mean tail-biting.

 

It looks very much like tail biting, and actually bettas cannot have melafix as a treatment because of their labryinth organ (from what I`ve read on multiple sources), so best to avoid it. You could add bettafix, it`s basically diluted melafix for bettas but it only does slight work for example my betta slightly (more of a scrape) cut himself on a plant and it only really prevented infections. For tail biters you just need to change stuff up every once and a while, for mine I change his around with water changes, (move around decor or replace it every so often) and it keeps him busy from biting his tail! I hope this helps!