It will grow back, but you need to watch closely for fungus. If it starts to look like tufts of cotton growing where the injury is, you will have to great with antibiotics or melafix and pimafix. Fungus doesn't go away on it's own, so just keep a close watch.
I've been treating daily with the melafix for the past two days, I did a 30% water change today, and added more melafix. The bottle said to treat daily for seven days, will that be enough, or should I treat longer?
Just follow the directions and hopefully you will see growth by the end of the treatment. Let us know when you see some growth. I don't think medicating a little longer past the 7 days will hurt anything.
It was my beta. I woke up the other morning and my platy that I bought when I first set up the tank was dead, and the black molly had a big chunk gone out of his tail. I know it was the betta cause she would chase the platy around sometimes. She also killed the female black molly. Needless to say, she has been removed to her own tank now. I just didn't want her to be lonely so I had her with my other fish. :'(
Well, the container she was in when I bought her said she was a female. That's all I have to go by. She seems to get along fine with my guppies and corys, but she didn't like the male black molly, or my male orange platy, which I think she killed, but don't know for sure since I didn't see her do it. :'(
The black molly's tail fin is growing back nicely.