Home » How Do Hermit Crabs Breathe?
can hermit crabs breathe underwater?

How Do Hermit Crabs Breathe?

Many new owners complain that their pet hermit crabs are inactive and die almost immediately.

This isn’t because hermit crabs are innately weak or have short life spans, as they can live up to 40 years in the wild. It’s just that hermit crabs need the right type of environment to breathe.

All hermit crabs breathe oxygen and need saltwater to get it. Hermit crabs breathe through their gills, but these must be kept damp.

Marine hermit crabs have large gills that transfer oxygen into the blood and convert it to carbon dioxide. This is then expelled through the mouth.

Land hermit crabs obtain oxygen from humid air and can’t breathe underwater.

Without sufficient water and humidity, terrestrial hermit crabs will suffocate and die.

Do Hermit Crabs Breathe Air or Water?

Hermit crabs breathe air through their gills but need water to be able to do so.

Their gills vary in size, depending on whether hermit crabs live primarily on land or underwater. As a rule, the larger the gills, the longer that hermit crabs can spend underwater.

All hermit crabs must spend time in saltwater. Marine hermit crabs live underwater, and terrestrial hermit crabs spend 95% of their time on dry land. However, they still need to bask in the water occasionally.

As per the Journal of Experimental Marine Biology and Ecology, exposure to saltwater leads to an adjustment of the hermit crab’s breathing rate. This is because oxygen reacts to water in the gills. The wetter the gills, the more oxygen reaches blood vessels.

This leads to differing behaviors. Those that live underwater will spend little time on dry land. They only leave the ocean to seek food or shells, or escape predators. They return to the sea long before their gills dry out.

Terrestrial hermit crabs, meanwhile, submerge in water periodically. This is usually up to 20 minutes at a time. This is partly a chance for the hermit crab to bathe. It also dampens the gills and stores water in the shell, which minimizes the risk of suffocation.

Hermit crabs have a unique physiology that enables them to store and retain water. Terrestrial hermit crabs will obtain moisture from the ground. To keep them alive, they must have access to a constant source of water.

What Else Do Hermit Crabs Need to Breathe?

In marine hermit crabs, the provision of water is sufficient for breathing. Provided that you maintain an appropriate temperature and salinity, and the water is clean and filtered, marine hermit crabs will thrive.

However, land hermit crabs need external water sources—place two ‘swimming pools’ of water in the tank. One should be filled with fresh water; the other sprinkled with marine salt. Never use table salt as the iodine within is toxic. This water must also be wholly dechlorinated.

Humidity and temperature are also critical to breathing in land hermit crabs. Most owners follow the 80/80 rule – humidity of 80% and a temperature of 80 degrees. This suits tropical hermit crabs that are used to a warm climate. The humidity introduces moisture to the air.

can hermit crabs drown?

Get a hygrometer to measure humidity. Use a misting spray to apply more, if necessary. Check that your hermit crabs are not too cold or overheating, too. Captive hermit crabs need a habitat that mirrors their natural surroundings.

The air surrounding your hermit crabs must be clear. Hermit crabs are delicate and can be harmed by fumes. As per American Zoology, land hermit crabs are more reliant on breathing carbon dioxide than pure oxygen. Alas, too much C02 remains dangerous.

This means that you should avoid spraying or using chemicals around a hermit crab enclosure. Avoid air fresheners, antiperspirant sprays, or anything that could contain CFCs. Assume that your hermit crabs will breathe in anything that you add to the atmosphere.

Signs That Hermit Crabs Are Suffocating

Monitor the hygrometer and thermometer. Ensure that the tank’s humidity level never drops below 80%, and the temperature does not get too high. Also, keep an eye out for these behavioral symptoms:

  • Lethargy
  • Labored movements
  • Loss of appetite
  • Constant hiding
  • Leaving the shell to cool off
  • Refusing to burrow
  • Shedding limbs
  • Skin fading to a dull gray

If you suspect that your hermit crabs are suffocating, relocate them to a new enclosure. One-by-one, place the hermit crabs in water for 10 minutes each. This will dampen the gills and aid breathing.

The damage may have been done. The health of suffocating hermit crabs will deteriorate over some time – suffocation does not lead to instant death. It’s a slow and steady demise.

Can Hermit Crabs Breathe Underwater?

As you’ll be aware, the chemical formula for water is H2O. This means that one water molecule contains two hydrogen molecules and one oxygen. As a result, oxygen is less concentrated in water. The air is around 21% oxygen; water is just 1%.

This is not a problem for aquatic hermit crabs. They have large, prominent gills, found close to the front pair of walking legs. They absorb oxygen from the water, transferring this to the gills.

Oxygen reacts with the blood of hermit crabs. They release carbon dioxide through the mouth, which is why marine hermit crabs appear to blow bubbles. This how marine hermit crabs breathe underwater. They can breathe out of the water as long as the gills are damp.

Terrestrial hermit crabs lack this ability. This is because they have much smaller gills than their marine brethren. These gills are also stiff and far less flexible. The gills can be overloaded with water. This is the equivalent of the lungs flooding with fluid.

As a result, land hermit crabs do not breathe underwater. Instead, they hold their breath while submerged in water. Hermit crabs can hold their breath much longer than humans. It is believed that hermit crabs can hold their breath for anywhere from 15-60 minutes.

How Long Can Hermit Crabs Stay Underwater?

As per Comparative Biochemistry and Physiology, hermit crabs experience breathing difficulty with prolonged exposure to the wrong environment. Marine crabs need constant access to water, while land hermit crabs should remain predominantly dry.

Nobody can be certain as to how long land hermit crabs can stay underwater. This varies between hermit crabs. It all depends on how developed the hermit crab is, and its overall health.

Hermit crabs can breathe underwater for around 20-30 minutes. Some hermit crabs, especially juveniles, will struggle after 10 minutes. Others can remain underwater for as long as 60 minutes.

Most hermit crabs have an innate sense of how long they need to remain submerged. You certainly cannot deny terrestrial hermit crabs water as a safety precaution. You will need to take precautions against drowning.

Can Hermit Crabs Drown?

Marine hermit crabs will never drown. As long as the temperature and salinity are appropriate, they will flourish in water 24/7. There is no need to remove aquatic hermit crabs from a marine tank.

It’s different for terrestrial hermit crabs as they cannot breathe underwater. Land hermit crabs grow woozy and disoriented when underwater for a prolonged period. Like humans, hermit crabs can only hold their breath for so long.

At this stage, hermit crabs seek to be able to get out of the water. If they cannot do so, drowning becomes a risk. They still need pools for bathing, drinking, and gill moisture.


Ramps in and out of the water are the easiest way to prevent drowning. If hermit crabs have simple access to water or dry land, they will use it.

Plastic canvas is the best material to use. This will not rust or rot in water, and it’s inexpensive. Cut the plastic to size and consider reinforcing it to hold the weight of your hermit crabs.

Avoid using metal as this will rust and release dangerous chemicals. Wood is also best kept separate from water. If it starts to rot, it may bend or break.

Appropriate Water Depth

You should also avoid providing too much water. Hermit crabs do not swim. They wander the floor of a pool or other water source. Once done, they will climb out. Deep water is just creating needless risk.

A pool needs to deep enough for hermit crabs to submerge fully. The average hermit crab will be around 3 inches in height, including the shell. This means that 5 inches of water will suffice.

how long can hermit crabs stay underwater?

How Do Hermit Crabs Breathe Under Sand?

In the wild, some hermit crabs live in intertidal environments. This means they could spend 12 hours around water and 12 hours on dry land per day. It depends on the location of the tide.

The hermit crabs will remain in cool, dark locations to prevent their gills from drying out. This may involve burying themselves under the sand, especially during the day.

Captive hermit crabs spend much of their time buried. While molting, hermit crabs remain submerged under substrate for weeks or even months. Hermit crabs engineer a tunnel that provides a path to oxygen.

Hermit crabs investigate several spots before digging. This is testing the pliability of their sand. They will eventually dig a tunnel. This provides darkness and privacy while retaining an oxygen source.

It is important to choose the right sand for hermit crabs. Playground sand from a hardware shop is fine. If you’re prepared to spend more, you could also get a specialist aquarium sand from an exotic pet shop.

These sands are fine and will not collapse, so suffocating and the inability to emerge are not risks. Of equal importance is the ability of these sands to absorb moisture. You may notice your hermit crabs spilling their water on sand ahead of digging, which is normal behavior.

Understanding how hermit crabs breathe is critical to keeping them safe. Many captive hermit crabs endure a short, uncomfortable life due to mistakes that lead to suffocation. Ensure that captive hermit crabs have sufficient access to water and oxygen.