He can be bitting for several reasons- boredom, stress, or just because he can. I have also heard that if their owner goes away for a few days they can become depressed/lonely and bite.
Maybe he isn't happy with the new plant? If you can figure out ehy he was bitting, you may be able to stop him (The one in my siggy bites his fins off everytime I change the water. He's supposed to be a Halfmoon but his tail is about as long as a plaket)> if not, just keep the water clean and maybe use stress coat for your conditioner. Keep an eye on him for fin rot.
Unless your tap water is unfit for human consumption, the conditioner should be all you need to make it healthy for the fish. When I live in alaska, my tap water was horrible. Without conditioner the fish would be dead in less then 24 hours