My two cents: White Cloud Minnows rock my world. They are surprisingly gorgeous, peaceful, do fine in cool water that newts like, have interesting displays (especially the males), and are impossible to kill, unless they are small enough to be eaten by newts, which seems likely. =D I've seen really pale, washed out ones in the store -- find bright, colorful, active specimens, if you do decide to get some (although they brighten up under good conditions). I'd recommend two males and about five females. As for Bettas, they like really warm water, and from what I understand, newts do not. That seems like a problem.