Hermit Crab Care Myths

purple pincher hermit crab
purple pincher hermit crab

Hermit crabs are small, cute little invertebrates that steal our hearts with a wiggle of their antennae and their fun climbing adventures. And what's not to love about an animal that carries its seashell house around with it?

Unfortunately, these critters are one of the most misunderstood animals in the pet trade and are often incorrectly described as easy, cheap, or "throwaway" pets. In reality, however, hermit crabs require just as much effort as other pets to care for, and when done so properly, they can live for over 20 years!

Myths and improper husbandry advice abound, but have no fear: this guide will help you sift through all the false information.

MYTH: Any Cage Will Do (Including Wire Cages)

Hermit crabs are one of the few terrestrial animals who use gills to breathe. Because of this unique anatomical feature, they require an incredibly humid environment to survive. Wire cages simply do not work, and the only enclosure suitable for these animals is an aquarium. Covering the tank with a solid plexiglass lid is the best option, or a screen top can be sealed with plastic wrap.

  • Extra Tip: If you cannot afford an aquarium, a large plastic storage tote/tub can temporarily be used to house crabs. Also, save up! Stores like Petco routinely have a $1 per gallon sale during which aquariums only cost as much as the amount of water they hold (a 40 gallon tank costs $40, a 20 gallon tank costs $20, etc).

Example of a small crabitat suitable for two hermit crabs.
Example of a small crabitat suitable for two hermit crabs.

MYTH: Any Temperature/Humidity is Fine

Hermit crabs are tropical critters and heavily rely on the conditions in their environment in order to thrive. They need specific temperature and humidity levels or they will perish.

A warm temperature is best achieved by attaching a reptile heat mat to the the back (not the bottom) of the cage. The goal is to heat the air in the enclosure and not the substrate. In colder households, insulating the outside of the aquarium with a water heater blanket can help maintain the correct temperature.

Temperature requirements vary slightly depending on the species of hermit crab, but these are the basics:

at least 80%
This 40 gallon aquarium (with an additional climbing area) is sufficient for four hermit crabs.
This 40 gallon aquarium (with an additional climbing area) is sufficient for four hermit crabs.

MYTH: They Don't Need Much Space

Hermit crabs become stressed when overcrowded. They may be social animals, but they still need to be able to move away from their buddies for some alone time every now and then. In fact, a crab's survival during the molting process depends on it. (In preparation for molting, a healthy crab will seek seclusion by completely burying itself, which keeps it safe from other, potentially hungry, hermit crabs).

The enclosure needs to provide at least 10 gallons of space per crab. This allows enough room for molting, climbing, eating, sleeping, hiding, and digging. This means a 20 gallon aquarium is the minimum tank size for two hermit crabs.

Huge Hermit Crab Enclosure

A hermit crab buried in its burrow.
A hermit crab buried in its burrow.

MYTH: Just Use a Couple Inches of Sand

Having proper substrate is arguably one of the most important aspects of hermit crab husbandry. Crabs bury themselves when molting and heavily rely on the depth, consistency, and moisture of the substrate in order to survive. Crabs will not do well when only provided a couple inches of sand for substrate. They really, truly need the following:

  • Depth: Substrate depth should be at least half the tank's height. However, if the aquarium is shorter than 12 inches, then the substrate should be a minimum of six inches deep. Having deep substrate really is important, as the only way a molting crab can protect itself from other hermit crabs is to hide. If not buried deeply enough, a molting crab risks being dug up by its hungry, cannibalistic friends.
  • Materials: The best substrate for a hermie is a mixture of two materials: coconut husk bedding (found in the reptile section at pet stores) and kids' play sand (found at any local hardware store). The coconut husk bedding is an important component because it holds moisture and helps maintain a sand castle consistency for burrowing. For a proper mixture, it's suggested to use one part coconut husk bedding to every five parts kids' play sand.

Do NOT use the calcium sand products sold in pet stores.

Calcium sand has cement-like properties once it becomes wet and then dries. There are many horror stories of pet owners who have had to save their hermit crabs from being glued inside their shells due to calcium sand. Avoid this product!

This hermit crab is munching on chia sprouts that grew from seeds planted in the tank's substrate.
This hermit crab is munching on chia sprouts that grew from seeds planted in the tank's substrate.

MYTH: Crabs Eat Store-Bought Pellets

Crabs will eat almost anything, but not commercial hermit crab diets. The pellets and powders sold in pet stores should be avoided because they contain ingredients harmful to crabs (like copper).

A balanced diet with lots of variety keeps crabs healthy. Calcium-rich food should be provided often, as well as protein and fats.


  • fresh and dried fruits and veggies such as apple, bell pepper, jalapeno, pomegranate, berries, mango, papaya, grapes, banana, orange, coconut, kale, lettuce, squash, cucumber, carrot
  • fats such as peanut butter, coconut oil, sunflower seeds, almonds
  • proteins such as mushrooms, shrimp, fish, meal worms, dead crickets, bloodworms, boiled egg
  • calcium-rich foods such as oyster shell, egg shell, shed snake skin, cuttlebone
  • other: kelp, rice, chia seeds, spirulina, leaf litter, worm castings

Example of a typical meal.
Example of a typical meal.
These water dishes are four inches deep. Note the ramps and climbing surfaces, which allow crabs to easily enter and exit the water.
These water dishes are four inches deep. Note the ramps and climbing surfaces, which allow crabs to easily enter and exit the water.

MYTH: Use Shallow Water Dishes with a Sponge

In the wild, hermit crabs submerge themselves in the ocean to reproduce. They also have access to both freshwater and saltwater. In captivity, they require that all these needs be met.

  • Provide both a freshwater and saltwater pool.
  • Tap water is perfectly fine to use as long as it is made safe using a water dechlorinator. The only brand proven to be safe for hermit crabs is Seachem Prime (available in the fish section at most pet stores).
  • Saltwater should be mixed using marine aquarium salt. Do not mistakenly use freshwater aquarium salt (yes, this product exists!). The best brand to use is Instant Ocean, and it can be found in the fish section of most pet stores.
  • Crabs will not drown in deep water dishes as long as they're able to climb out, and most hobbyists agree that hermies benefit from being able to completely submerge themselves.

Some pet owners complain that their hermit crabs drowned in the water dish, but this is very unlikely. When a crab is sick, distressed, or dying, the first thing it does is head for the water dish. Many crabs pass away in their water dishes because something else was wrong. They did not drown!

Painted shells are toxic!
Painted shells are toxic!

MYTH: Painted Shells are Fun and Safe

Hermit crabs are actually quite picky about their shell choices, and they even modify their shell to better suit their needs by chewing the edges and carving out the inside. Because of this, painted shells are toxic to crabs! Ingesting paint isn't safe for us, and it definitely isn't safe for a fragile invertebrate either.

  • At least six appropriately-sized shells should be available at all times for each crab. For example, two crabs require 12 shell choices, three crabs need 18, and four need 24. If hermies are not given enough options, they will fight and may even kill each other.
  • Different species of hermit crab tend to prefer different types of shells. Keep this in mind when shopping for shells!

MYTH: Crabs are Pets You Can Hold

Hermit crabs are not only fragile animals who can suffer major injuries if dropped, but as mentioned earlier, they're creatures who live on land but breathe through gills. Removing a hermit crab from its humid, warm enclosure into a cooler, drier room causes stress, and these animals do not handle stress well.

MYTH: Crabs are Cheap Pets

Now that the common myths have been busted, it becomes quite obvious that providing hermit crabs with the care they need is most definitely NOT cheap. The initial purchase of the enclosure, decor, substrate, water dishes, and food will cost $60-$100, and that doesn't even include the price of the crabs! And as a hermit crab grows, it will require bigger, more expensive shells. Jumbo-sized crabs will eventually require difficult-to-obtain shells that can cost up to $20.

Summary of Proper Hermit Crab Care
Summary of Proper Hermit Crab Care

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