What Do Hermit Crabs Eat? Food, Calcium and Water

Quick answer: land hermit crabs are omnivores and scavengers. Feed a varied mix across the week: fruit and vegetables, leaves, a protein such as dried shrimp, fish or insects, and a calcium source that stays in the tank, with a dish of fresh water and a dish of salt water. Put food out in the evening and lift out what is left in the morning.

We do not sell hermit crabs, but much of what they eat is already on our dry goods shelf. This guide covers what land hermit crabs eat in the wild, what to feed them at home, which of our foods fit and what keepers leave out.

What Hermit Crabs Eat in the Wild

Land hermit crabs kept as pets include the Caribbean hermit crab (Coenobita clypeatus) and the Ecuadorian (C. compressus). In the wild they scavenge along tropical coasts, eating fallen fruit, seeds, flowers, leaves and other plant matter, whatever the tide leaves behind, dead animals, insects and even other animals' droppings. Plant matter is a large part of what they eat.

Feed for Variety

Nobody has worked out a hermit crab's full nutritional needs through controlled feeding studies, so keepers feed for variety: what the crabs eat across a week matters more than any one meal. A vet-written care sheet suggests feeding once a day, in the evening, and lifting out the leftovers the next morning. Use non-metal dishes that do not soak up water, such as glazed ceramic or hard plastic.

Protein: Shrimp, Fish and Insects

The protein foods keepers use include dried shrimp, krill, fish and insects such as mealworms. Our dried shrimp are whole, sun-dried shrimp. Our dried large sprats are whole dried fish with a strong smell, so offer a small piece at a time and clear it by morning. For insects, our dried calciworms are dried black soldier fly larvae, and our dried silkworm pupae are rich, at 27 per cent fat, so keep those to the occasional piece. Rotate them rather than leaning on one.

A pile of dried silkworm pupae, dark brown and ridged, on a white surface

Fruit, Vegetables, Leaves and Seeds

The plant side of the diet covers fruit, vegetables, leaves, flowers and seeds. Wash shop-bought fruit and vegetables, and only offer leaves gathered well away from sprayed ground. Our freeze-dried garden peas are one ingredient, garden peas, with nothing added. Our broadleaf leaf litter and large magnolia leaves are dry hardwood leaves that can stay in the tank for the crabs to pick over. As with any leaves, bake or freeze them before they go in: about 100°C for at least 30 minutes, or at least a week at -18°C or colder.

Calcium

A hermit crab rebuilds its exoskeleton at every moult, and keepers leave a calcium source in the tank all the time. Cuttlebone, oyster shell and crushed eggshell are the usual choices. Our crushed oyster shell is at least 95 per cent calcium carbonate, supplied crushed with nothing added, and it is best kept in a dish of its own. After a moult the crab eats its old exoskeleton, so leave it where it is.

Crushed oyster shell in grey, cream and brown fragments

Water: Fresh and Salt

Hermit crabs need two water dishes: dechlorinated fresh water, and salt water mixed from marine aquarium salt. The same vet-written care sheet gives a specific gravity of 1.021 to 1.026 for the salt water. UK tap water is treated with chlorine, chloramine or both, depending on where you live, so use a conditioner that says it treats both. Our article on whether tap water is safe explains why.

What to Leave Out

Anything from sprayed ground. Fruit, vegetables and leaves that may carry pesticides or weedkillers.
Foods listing ethoxyquin or copper sulphate. Many keepers avoid them. Ethoxyquin is a preservative used in fish meal. The evidence behind the rule comes from tests on other invertebrates, such as water fleas, not on hermit crabs, but it is an easy rule to follow: read the ingredient list.
Strongly scented herbs and essential oils. Many keepers leave them out.
Yesterday's leftovers. Lift out uneaten food every morning.

Stick to plain foods: nothing seasoned, sauced or cooked with salt. The vet-written care sheet lists fish flakes as an occasional treat, but ours are not in this guide: their ingredient list includes antioxidants without naming them, so we cannot rule ethoxyquin out.

A Note on Keeping Hermit Crabs

Hermit crabs can live for more than ten years, and UK law counts decapod crustaceans, the group hermit crabs belong to, as sentient. A varied diet, offered fresh each evening, is a big part of keeping them well.

Frequently Asked Questions

What do hermit crabs eat?

A varied mix of fruit, vegetables, leaves and seeds, with animal protein such as shrimp, fish or insects, and a calcium source that stays in the tank.