Hi Kimberly, and welcome to the forum.

You're right, you can't continue with Goldfish, they're toxic!
http://www.thamnophis.com/caresheets...INASE_PROBLEMS
Sometimes it requires a little time and patience to wean them onto mice. The fact that he is biting it shows that he is interested, I'm sure he'll take it if you keep trying and make sure you are scenting thoroughly. In the meantime I would recommend you switch to a different fish.