What Can Hermit Crabs NOT Eat? (Toxic Foods to Avoid)

Hermit crabs cannot eat onions, garlic, citrus fruits, table salt, commercial pellets with preservatives, dairy, chocolate, candy, pesticide-treated produce, and anything seasoned or processed. While hermit crabs are natural scavengers that eat a huge variety of foods, the wrong item can make them seriously sick or worse. The good news is that the unsafe list is much shorter than the safe list. Once you know what to avoid, feeding becomes easy and stress-free. Here is the complete breakdown of what not to feed your hermit crabs and why.

The Most Dangerous Foods (Truly Toxic)

These foods can cause real harm and should never go in the tank:

• Onions (all types). White, red, yellow, spring onions, and shallots are all toxic to hermit crabs. Onions contain compounds that are fatal to invertebrates. Even small amounts can cause problems.
• Garlic. Like onions, garlic contains compounds that are harmful to invertebrates. Avoid all forms including fresh garlic, garlic powder, and garlic salt.
• Table salt. Regular table salt contains iodine and anti-caking agents that are toxic to hermit crabs. Too much iodine is especially dangerous. Only use marine-grade aquarium salt (like Instant Ocean) for their salt water pool.
• Commercial pellets with preservatives. Most hermit crab foods sold in pet stores contain ethoxyquin and copper sulfate – both are toxic to invertebrates. Check the ingredients. If it lists fish meal, it likely contains hidden ethoxyquin that does not have to appear on the label.
• Pesticide-treated produce. Fruits and vegetables sprayed with pesticides can poison your crabs. Wash everything with dechlorinated water before serving, or buy organic.

Bonus: What Do Hermit Crabs Like?

Foods That Are Harmful or Best Avoided

These may not be immediately toxic, but they can cause health problems over time or are simply not suitable for hermit crabs:

• Citrus fruits (oranges, lemons, limes, grapefruit). Highly acidic and most crabs refuse to eat them. Citrus tree bark and leaves also contain natural insecticides that are toxic. Safest to skip citrus entirely.
• Dairy (milk, cheese, yogurt). Hermit crabs are lactose intolerant and cannot digest dairy products. Feeding dairy can cause digestive problems.
• Chocolate. Contains theobromine, which is toxic to many animals including hermit crabs. Keep all chocolate and cocoa products away from the tank.
• Candy and sugary processed foods. Artificial sugars, dyes, and preservatives are all harmful. Hermit crabs enjoy natural sweetness from fruit – they do not need processed sugar.
• Avocado (skin and pit). The flesh is considered safe by some keepers, but the skin and pit contain persin, which is toxic to many animals. To be safe, most keepers skip avocado completely.
• Rhubarb. Contains high levels of oxalic acid that can be harmful to hermit crabs.

Toxic Plants and Wood

If you use live plants or wood in your tank, make sure none of these are included. Some are commonly sold in pet stores and garden centers:

Toxic Plants	Toxic Wood	Other Dangers
Ivy (all types)	Cedar	Painted shells
Oleander	Pine	Metal dishes
Holly berries	Eucalyptus	Tap water (chlorine)
Mistletoe	Treated lumber	Sponges (bacteria)
Azaleas	Yew	Scented candles nearby
Lilies	Hemlock	Cleaning spray fumes
Lucky bamboo	Juniper	Insect repellent sprays

Key rule: Cedar and pine are the most common mistakes. Their natural oils are toxic to hermit crabs and can cause breathing problems. Only use safe woods like driftwood, cork bark, cholla wood, or grapevine in the tank.

Bonus: What Fruits Can Hermit Crabs Eat?

Hidden Dangers in Common Products

Some of the most harmful things for hermit crabs are not foods at all – they are products that owners use without knowing the risk:

• Ethoxyquin. A preservative found in most commercial hermit crab pellets and fish meal. It is toxic to invertebrates but does not always appear on the label because it is added during fish meal processing, not by the pet food company.
• Copper sulfate. Another common preservative in commercial crab food. Copper is highly toxic to crustaceans even in small amounts.
• Tap water. Contains chlorine and chloramine that damage hermit crab gills. Always use a water dechlorinator before putting tap water in the tank.
• Scented candles and air fresheners. Airborne chemicals from candles, plug-in fresheners, and cleaning sprays near the tank can enter the humid air and harm your crabs. Keep the tank in a room free from strong airborne chemicals.
• Painted shells. The paint chips over time and the chemicals leach into the crab’s skin. Only use natural, unpainted shells.

How to Check If a Food Is Safe

Not sure about a specific food? Run through this quick checklist:

• Is it organic or pesticide-free? If not, wash it well with dechlorinated water before feeding.
• Is it plain and unseasoned? No salt, butter, oil, spices, sauces, or dressings. Plain food only.
• Is it free from preservatives? Check labels for ethoxyquin, copper sulfate, and BHT. If any of these are listed, skip it.
• Is it a known toxic food? Check it against the lists above. When in doubt, do not feed it.
• Is it fresh or frozen (not canned)? Canned foods contain added salt, sugar, and preservatives. Use fresh or frozen instead.

Conclusion:

The toxic food list for hermit crabs is short: onions, garlic, table salt, citrus, dairy, chocolate, pesticide-treated food, and commercial pellets with preservatives. Add cedar and pine wood, painted shells, tap water, and airborne chemicals to the avoid list and you have covered almost every common danger. Everything else – fresh fruits, vegetables, protein, calcium, and natural treats – is fair game. Keep it fresh, keep it plain, and keep it varied. Your crabs will be healthy and happy for years.

Bonus: How to Feed Hermit Crabs

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