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Avoid processed foods. Make some hardboiled eggs. Pop some popcorn. Give your crab cuttlebone. Try adding spirulina powder. Make sure they have clean water.
When selecting food for your hermit crab, understand that your crab can eat almost any whole, unprocessed food. Food with added table salt and added sugar (such as chips, cookies, or fast food) can have a negative impact on your crab. These foods can cause digestive distress or even illness in your crab. Do not give your crab processed food. Another favorite source or protein for hermit crabs is hardboiled eggs. This can be served as part of a meal, or as a snack. Be sure to let it cool off quite a bit before offering a hardboiled egg to your crab.  Simply place eggs in a small pot and cover with water. Bring to a boil and let simmer for 8 minutes. Some crabs may also enjoy scrambled eggs. Popcorn is a wholesome food that can be given to your hermit crab as a treat. The healthiest popcorn is air-popped without oil, but any plain popcorn (without butter) can be an enjoyable snack for your hermit crab. A cuttlebone is the flattened oval internal skeleton of the cuttlefish. Dried cuttlebones can be purchased at pet stores to feed birds, hermit crabs, and other animals. Place a whole cuttlebone in your crab’s tank for him to nibble on, or crush one up and include it in his meal. Spirulina powder is a dense super-food powder made from blue-green algae. This powder can be added to your crab’s food to supplement him with amino acids, protein, iron, and vitamins B, C, D and E. Spirulina powder is available at any health food store. Provide clean, filtered water for your crab to drink. Additionally, make a saltwater bowl available to him about once a week. You will want to replace the water in the fresh water dish each day to make sure your crab stays healthy.