Most large grocery stores have a good selection of frozen marine shrimp, crab, lobster, mussels, squid, and fish to chose from. It may be necessary, especially at first, to skewer frozen food and swim it around the tank to get a feeding reaction. If you have been feeding frozen food for a while and are having problems feeding try temporarily switching to live food. Live freshwater crustaceans such as freshwater shrimp, crayfish and fish can also be used. Although live freshwater foods are not quite as nutritious as their marine cousins, cephalopods will grow and thrive on them, and they do elicit a healthy feeding response.
Cuttlefish do eat a lot, but like most marine creatures they can be overfed.
A healthy cuttlefish that feels secure in its surroundings is very likely to 'beg' for food and train its owner to give it more than it needs - especially if it is being fed live food. Excess, uneaten food should be removed, as it will rot and may cause an ammonia spike. Proportions should also be reduced past the point where the little beast is able to eat everything. If your cuttlefish isn't eating very much of the frozen food that you are offering, switch back to live food for a while. Underfeeding can also be a problem.