Welcome to the forum, and sorry to hear you have a tailbiter. Those guys are hard to break of the habit. Moving him might help some, otherwise it may be a constant battle with him and keeping his water clean to avoid fin rot.
One thing I noticed in your first post, you mentioned you needed to go out and get water for a water change... what water are you using? Anything but tap water is actually bad for them.. they lack nutrients and minerals needed that the filter system for spring and distilled water takes out. It's always best to use tap water with water conditioner/dechlorinator. I know some store employees (grr) say to use distilled, and the cups at Walmart says spring water.. but those should not be used unless needed for specific balancing of parts of the chemistry and even then you only use a little bit.
Sorry if I read what you said wrong.. but just making sure!
Adding in AQ salt won't help the biting, and it won't help the healing since AQ salt can actually hamper the growth of the fin.. some may use it as a way of prevention.. but the best prevention is just clean water with water conditioner. If you want fin regrowth, Stress Coat is what you are after. You can either use it just as your primary conditioner, or you can add in a few drops along side of your conditioner. No need to put the extra stress and daily water changes for biting of the fins.. You don't want to use AQ salt unless you are using it as a treatment, it can cause problems for the fish's health long term, and he and the bacteria in the tank will become immune to the beneficial properties it does have if over exposed. So unless treating for rot, ich, etc.. it's not recommended to put in the tank.
Originally Posted by Curlyfatass
Hmm it's not an aggressive fish...
Some time if a fish get hungry...
They'll eat there own fin....
Aggression/hunger have nothing to do with tailbiting. It's usually stress and heavy fins, sometimes boredom. A lot will bite their fins in transport, some lose the habit once they get into a new enviroment, some stop then start again, and others never stop. The stress from the transport causes it, stress to a new home (going into a larger tank) can cause it as well. But moving to a new home can stop it as well.. if it's tail related it's because going from a small cup/tank to a larger one, their muscles aren't as strong and sometimes they feel the drag and will num it.
But pretty much you just never know when/if one will become one and only thing you can really do to prevent it is make his living as stress free and plenty of plants/caves as well as being in a part of your home that is used often so he can see and watch what is going on around him.