What sort of fish can live with a fire bellied newt?

I've read and heard of mixing disasters, and currently have one fire bellied newt living peacefully with a betta.. but I am upgrading to a 20 gallon instead of a 5 gallon and want to know if I should keep the newt and betta separate or if I can have the newt, beta and a couple other fish such as just regular gold fish without causing harm Sorry if I sound moronic I'm new at this.