Drop the ghost shrimp idea. Im pretty sure one of my rays could probably finish up all 200 in one go, if not, another one would finish the rest. Variety is the key. For now just get your ray eating on some worms, weather it be night crawlers or earthworms, practically the same thing. Maybe a month or two later, when its well fed, start weaning it onto other foods like market shrimp, pellets, fish fillet etc. You should be able to reach a point where you can practically feed your ray anything and it will happily eat it up. For example, I know many members, myself included, who are able to walk into a supermarket and pick up whatever is on sale knowing my rays will eat it. This saves you hell of alot of money in the long run when you try to feed rays.