I am not specifically familiar with sand sifters, but with other starfish, I've had success feeding clams. Go to you local market and purchase a couple clams. Freeze them. Now open one up and cut a piece off. (The freeze makes opening and cutting the clam a whole bunch easier.) Now put in some tank water to thaw for a couple minutes and now using forceps, place close to the starfish. If it's like the stars I've feed, they "smell" the clam and move to grab it. Folks don't realize that most starfish are meat eaters....not algae eaters.