I have 2 gargs that were the first corals in my tank. Thats about 5 years old. Any gargs with white polyps are non-photosynthetic. The purple gargs are. The more light you throw at them the faster they grow,IMO. They can be fed small foods, even flake food if it's crushed small enough. A turkey baster is the best way to feed them,IMO.
They frag vert easy with wire cutters, after the cut use the wire stripper part to remove the flesh from the center, and that can be super glued into a new hole in a rock.
Any thing else you want to know?