Aquarium Salt questions, need answers asap!

[AngelicScars]

Okay, I woke up and saw Castiel with fin rot today. I have no idea how he got it. Anyway, I am giving him a salt bath in the next few minutes. If possible, I need these questions answered before his salt bath is over. Here are my questions:
Should I put aquarium salt in his tank?
If so, how much in a 5 gallon?
Should I remove the biofilter?

I'm thinking about putting him in a quarantine, but I'm not sure. I 50% his tank on Thurs, should I go ahead and 50% or more his tank again before putting him back in?

Thanks for any and all the help!

[neenjar]

I would do the bath in quarantine. a little salt in the main tank with water changes is fine.

A 50% change before returning him to the main tank is a great idea!

I would not do anything to the main tank but a water change. Maybe replace the filter media if it is due.

[AngelicScars]

The funny thing is, I just cleaned his tank and replaced the filter not even 2 weeks ago.
I'm going to go ahead and 50% out his water. I guess I can just add a little salt to the tank.
Thanks for the quick reply, I really appreciate it!