Please please please do more research on fish before buying them if these just went into the 20gal you posted about before. Mixing damsels (and even having 2+ of the same type) in a nano almost always results in one or more fish being torn up. Even if the two fish are ok at first while they are immature, they will not stay friendly towards each other as they grow.
As much as you already attached to Fred and Barnabus, I'd agree with Donya.... In the long run (short long run) neither you nor you fish will be happy. A pair of ocealaris clowns would be one appropriate choice. There are many different varieties of these beautiful, fairly peaceful fish... I love the black and whites.