Treating Tail Biting?

[prosthetik]

So Im getting my first rescue Betta on Thursday. He's a beautiful red male VT with blue/purple iridescent scales on his body.
He's been at the store that I have my female on order from for a few weeks now, & last week I noticed his dorsal fin is bitten off almost completely off & parts of his caudal fin are missing too.

I've been tossing over the thought of rescuing him & I've decided Im going to do it. Im bringing him home with me when I get my girl on Thursday.

So the question is, which is the best way to treat tail biting? I'll get him his hospital tank the same day as well. I dont really need a heater as its summer & the water temp is like 80 degrees. Im prepared to do daily water changes if necessary & I have API Stress Coat & Aquarium Salt handy.

But beyond all that Im really excited for my first rescue!

[Tikibirds]

It would depend on why he is bitting in the first place.
It's possible that he is stressed out in the shop and once in a warm, tank he will stop. I would get some silk plants or real plants to help him feel secure. I like to have at least one, big oversized plant in my tanks - so they can swim around it and rest on the leaves at the surface. He could be stress, bored, angry or just does not like long fins.

Other then that, clean, warm water is best for healing fins. Stress coat and aquarium salt can also be used. Use the salt for no longer then 10-14 days.

[Luxavior]

Another issue could be that he is possibly under-fed

[Fabian]

I don't think you can treat tail biting.
Tail biting is caused by heavy fin which makes the betta hard to swim.
You can only prevent it.
Try lowering the water level and add some medication to prevent fungus growth.