A warty is a fish that will do better on live foods, and I find long term success on a dead only diet literally impossible. I strongly advise against feeding any salt water fish, it's not a question of "if", they will be guaranteed to contract a disease from a salt water fish. Anglers are susceptible to ich and obviously internal parasites are a scourge. You absolutely can not count on themn taking dead food, and if they do, it can be short lived. And for some reason they just don't thrive on a dead diet. And you will never completely see their awesome and cool personality if they are not hunting for food.
At that size ghost shrimp and feeder guppies are likely going to be the best available choice of foods. Feeder guppies are tough as they can be somewhat buoyant in salt water. Getting him the food can be tricky, if you are serious I have some tricks to herd the food to him so he can catch them. Mollie babies would be better than guppies, it's even easy to breed your own. Depending on how involved you want to be, breeding mollies can be a fun project. Warty's will not likely ever get large enough to eat the mollies sold at Petco. Fancy guppies are another good choice of foods, and will likely be a good choice when he gets over 2". Peppermint shrimp, if kept in the store;s "invert only" salt water system would be another good food for a larger warty.
Initially at that size you can feed him a couple times a week, really until he is about 2", then go to once a week, and eventually every 10 days. Feeding a few small items is better than a really large item, even though physically he can get them down. A gorge/fast routine is better than feeding more often. feed him until you see a good bulge in his belly, then give him a few days to digest. Overfeeding may likely be the #1 cause of death for these guys, feeding too often may even more deadly than feeding too much.