All hermit crabs are born in the ocean. The majority of them remain living underwater for life. Some breeds evolve to live on land, and these account for many of the hermit crabs kept as pets in the United States.
Aquatic hermit crabs cannot breathe for long on land, while terrestrial hermit crabs cannot breathe underwater. While land hermit crabs need water for drinking and bathing, they prefer to stay dry most of the time. They dampen their gills to aid breathing, but otherwise, avoid submersion in water.
Hermit crabs can live on land, or they can live underwater. For the most part, these are mutually exclusive lifestyles. Never force a terrestrial hermit crab underwater and leave aquatic hermit crabs in their wet habitat.
Are Hermit Crabs Land or Sea Animals?
They can do both, but never at the same time. As explained by Current Biology, there are over 800 disparate species of hermit crab. The majority of wild hermit crabs are aquatic, living exclusively in water.
Of these aquatic hermit crabs, only one species lives in freshwater. Known as clibanarius fonticola, this hermit crab is native to the Pacific island country of Vanuatu. All remaining species of aquatic hermit crabs live in oceans across the globe.
Not all hermit crabs are aquatic, though. Some breeds live on land and are unable to breathe underwater. These are the most common hermit crabs sold as pets in the United States.
Despite this, all hermit crabs start life in the sea. When a land hermit crab is ready to give birth, she casts hundreds of eggs into the ocean. These eggs explode in saltwater and zoea – hermit crab larvae – hatch. Zoea that survive make their way to the surface and evolve into terrestrial hermit crabs.
If you have a land hermit crab, it cannot live in water. The crab will drown in less than an hour. Equally, marine hermit crabs are incapable of surviving on dry land.
How to Tell if Hermit Crabs are Terrestrial or Aquatic?
If you spot hermit crabs in the wild, their habitat will tell you all you need to know. If the hermit crab is scurrying on the seafront, it will almost certainly be a land crab. If you get a hermit crab from a seafront gift store housed out of the water, it is a land crab.
There are some aesthetic differences between marine and terrestrial hermit crabs. Both types of hermit crab have 10 legs. In a land hermit crab, these will be one, uniform color. Red or purple are common hues. Marine hermit crabs usually have speckly or stripy legs.
This is where the differences in appearance end. There are few variations in behavior between marine and land hermit crabs, either. Both like to live in colonies and have similar diets. All hermit crabs are omnivorous scavengers, eating whatever they can find.
Land hermit crabs are easier to care for. They still have complex needs, but you will not need to manage water temperature and quality. You must replicate the hermit crab’s natural habitat as much as possible.
Marine hermit crabs still make great pets, especially if you have a fish tank. Hermit crabs can live side-by-side with seawater fish and help keep an aquarium clean by eating algae. It is inadvisable to adopt marine hermit crabs as a first pet, though.
Caring for Aquatic Hermit Crabs
If you’d like to maintain a saltwater fish tank, aquatic hermit crabs are a great addition. Alternatively, they can live by themselves in an aquarium. You’re sure to be fascinated by watching your hermit crabs either way.
You’ll be able to get marine hermit crabs from most underwater pet specialists. Before you even consider adopting marine hermit crabs, you must, ensure you understand their needs. These include:
- Substrate for burrowing – this is where hermit crabs sleep and molt
- Reefs to recreate the natural habitat of hermit crabs
- Hiding places and toys for recreation
- A selection of shells, in case the hermit crab wants to change shelter
- Saltwater – marine hermit crabs must live in saline water. This means you’ll need to ensure any tankmates are compatible
- A second aquarium for when water is being changed or the tank cleaned
Marine hermit crabs come in two core sizes. Dwarf breeds usually peak growth at around an inch. Other hermit crabs will grow to around two inches.
An aquarium must be at least 10 gallons in size. Ideally, aim for larger, especially if you also keep fish within. Remember, hermit crabs are used to having an entire ocean to traverse. The more space hermit crabs have, the less likely they are to fight.
Setting Up an Aquarium
Setting up an appropriate aquarium is the most essential part of hermit crab care. The water must be just-so to keep these animals healthy. This table describes the needs of hermit crab tank water.
|Temperature||72-81 degrees Fahrenheit. Hermit crabs flourish at the cooler end of this scale|
|Salinity||31 – 35 parts per million. Use marine salt to achieve this – never table salt|
|pH||Between 8.1 and 8.4. Use baking soda to increase pH if necessary|
|Carbon||Carbon hardness should be between 150 and 215 parts per million|
|Nitrates||Below 10 parts per million. Ensure your water filter maintains this nitrate level|
If you need help setting up an aquarium for hermit crabs, seek advice. Hermit crabs are not the hardiest animals. They need a particular environment to survive. Above all, ensure the water is kept clean. Hermit crabs loathe living in unsanitary conditions.
Can Hermit Crabs Survive on Land if They Live Underwater?
Marine hermit crabs can survive out of water for a short period. Both land and marine hermit crabs have gills. The difference is that land hermit crabs also have lungs. This means they obtain oxygen from fresh air. Marine crabs gain their oxygen from the water.
Marine hermit crabs will rarely spend time on the shore. If they do, they rapidly retreat to the water. That said, hermit crabs rarely live in particularly deep waters. Most marine hermit crabs will be found within 450 feet of the ocean surface.
Marine crabs can breathe on land for as long as their gills are wet. This means that marine hermit crabs may make fleeting trips to the shore to scavenge for food. They may also be seeking a new shell. This is less likely, though.
Land hermit crabs are instantly attracted by pheromones released by a dying hermit crab. This scent informs serving crabs that a shell is about to become vacant. As land hermit crabs are at constant risk of attention from predators, a solid shell is a must.
Marine hermit crabs also need shells. As explained by Crustaceana though, aquatic crabs do not seek shells that were previously occupied by fellow crabs. They prefer to locate shells within the ocean. Marine crabs may also claim shells from underwater mollusks.
Caring for Land Hermit Crabs
If you picked up hermit crabs from a seafront gift shop as a vacation souvenir, you have terrestrial hermit crabs. These are much more common as pets than marine hermit crabs. The latter are typically retained by fish keepers as clean-up crew in an aquarium.
If you have land hermit crabs, they cannot live underwater. You can still house the hermit crabs in an aquarium. You just need to keep the environment dry and humid. Terrestrial hermit crabs are good pets, but not as low maintenance as you may have been told.
To keep your hermit crabs happy and healthy, you must mimic their natural environment as much as possible. That means setting up the perfect habitat before bringing your hermit crabs home.
Creating a Habitat for Land Hermit Crabs
Setting up a home for terrestrial hermit crabs comes with several non-negotiables. They need a solid, enclosed enclosure. Never use a barred cage. This allows too much humidity to escape the habitat. The perfect land hermit crab habitat contains the following:
- Around 6 inches of a substrate. Use sand or soil, never grit or gravel
- Humidity of 80%. Track this using a hygrometer. Apply a misting spray whenever humidity drops below 80%
- Temperature of around 80 degrees Fahrenheit
- Hiding places, such as rocks
- Climbing apparatus. These include rocks, in addition to vines or plants
- Other toys for recreation
- A light-dark cycle as they need 12 hours of light and 12 hours of darkness
Most importantly, provide companionship. Despite their name, hermit crabs are social and live in colonies in the wild. Hermit crabs grow lonely and depressed when they live alone.
You should spot clean a hermit crab enclosure daily and complete a deep clean every three months. Escalate a deep clean to ASAP if you spot any mold in the tank. Hermit crabs are often killed by bacterial infection.
All hermit crabs are nocturnal. You will notice this more with land hermit crabs. Avoid disturbing these animals during daylight hours. If your hermit crabs are burrowed under their substrate, they want to be left alone. They will surface and become active after dark.
Do Land Hermit Crabs Still Need Water?
Just because your hermit crab lives on land, it does not mean it can live without water. Terrestrial hermit crabs need both fresh and saltwater sources. These are used for bathing and drinking. Hermit crabs like to have a choice of both water sources.
When bathing, hermit crabs submerge themselves in water completely. This dampens the gills to aid breathing, cleans the abdomen, and stores water in the shell.
Hermit crabs need to be able to escape their bathwater without difficulty. Provide steps or something for the crab to grip. If a hermit crab finds itself trapped in water, it will drown. If this concerns you, consider the use of sponges instead or in addition to a bath.
You can create saltwater at home using marine salt. This is available from any reputable exotic pet store. Never use table salt, as this contains dangerous chemicals that will harm hermit crabs.
Equally vital is that you never use tap water for hermit crabs. This contains heavy metals such as copper, and chlorine. These are toxic to hermit crabs. Filter water or get it by the bottle.
If you take the latter approach, the bottle makes a new obstacle and toy for your hermit crab enclosure. Leave the cap on, though. Wild hermit crabs sometimes climb inside plastic bottles and grow trapped inside.
Do Land Hermit Crabs Ever Go in the Sea?
Terrestrial hermit crabs will dip in the sea on occasion. Wild hermit crabs do not have access to bathing or drinking water. This means they need to rely on natural sources of water. This means these hermit crabs stay close to the shore where possible.
Some land hermit crabs will prefer to use a puddle. This is safer for the crab. As per the Journal of Experimental Marine Biology and Ecology, some species of fish eat hermit crabs. In some cases, though, hermit crabs have no choice but to take their chances.
Land hermit crabs will not stay in the water any longer than they need to. Half an hour is the longest these crabs can breathe underwater. This is enough time to bathe, dampen the gills, and store water in the shell. This means the crab will not need to enter the sea again for a few days.