I've used small cacatuoides as dithers with shy dwarfs and that semed to work well. Neons etc are ok, but tend to swim in the upper water column, the apistos stay down low where they make good targets for the pair to defend against. I would also suggent using a few small corys like C. habrosis. They never seem to bother eggs or fry, and are good targets too. Watch to see if they are being too beat up, I had one killed by a pair of Nannochromis transvestites.