Leathers are pretty hardy, imo, you don't have to feed them directly, they will get what they need from the light and water, just good flow seems to keep them happiest. If it is a loose frag you can rubber band to a rock or wedge it somewhere until it attaches. Some zoos will take small bits of mysis but other don't need to eat and torch should be fed mysis or shrimp once a week is probably fine, some people don't feed them at all but they may grow better if fed.