you don't have to feed it, but the hammer will respond well to feedings and IMO euphillia (and most lps) seem healthier when fed regularly. once a week I typically (with pumps off) thaw some frozen food and spot feed all my lps, spray a little of the juices at the sps, and the fish will just eat whatever is floating around.
lps will typically eat just about anything they catch, I find they like good fresh frozen foods. they seem to really love the rod's I've been feeding lately.. but my euphillia regularly catch pellets or flakes floating by in the current..
after eating, lps typically look extra happy for a few days ime.