Usually people just let their hermits eat detrius, algea, and other stuff in the tank. I have never fed my hermit crabs or snails and have had some of them for a year.
I don't add anything specifically for my hermits. They clean up what doesn't get consumed by the fish. Feeding them may lead to an overfeeding of the tank.
I have several small hermits and Larry the lobster in my 150. I feed them Crab Cuisine (Hikari I think) every now and then. They love it and its fun to watch the shrimp go nuts. I hope you and Bob can share the affection that I and Larry have found! (I need to get out more)