I use to bred them with good success. The DD genetic is recessive compared to the other colors. When you inbred them (brother and sister), the babies are weaker. But you will get better results that way for the color only. The proper way to bred a healthy DD angelfish would be done through line-breeding. Most of the DD angelfishes out there have been inbred already. So to strengthen your genetic line and create a sustainable breeding project, you will have to breed the DD to a gold. The resulting babies will most likely be gold because gold is a stronger gene that the DD. You will have to grow up the babies and bred them back to the parent to create a decent quality fish. Part of the resulting off springs will be DD. I do not use the marble because sometimes the color will blend and create a fish that is not totally black. Some will be totally black. I don't prefer to use the silver because it is a stronger genetic trait than the gold. Line breeding that will get less percentage of DD off springs. That means the babies will have a stronger color that you don't want. Good Luck.