Target/dither fish are a good addition to any breeding set up, they work in two ways. The first is to help assure timid fish that the area is free of predators and safe to breed in, fish like Appistogramma species and Corydoras with small characins (tetras) as dithers would fall into this catagory. The second is for aggressive fish like central American cichlids, adding fast moving tough medium/large sized fish for the male to charge at helps a pair form a bond and gives the cichlids something to do rather than fight each other, tinfoil barbs and large silver dollar type fish make good target fish.
