hermit crab humidity requirements

Why Do Hermit Crabs Need Humidity?

Last Updated on: 8th October 2023, 02:01 pm

It’s estimated that somewhere between 800 and 1,000 different hermit crab species exist worldwide. They’re broken down into two types – land and marine.

While marine hermit crabs live and breathe underwater, land hermit crabs (terrestrial hermit crabs) can’t breathe underwater and can only survive in a dry but humid environment.

The tank’s temperature and humidity are crucial to hermit crabs’ survival. 

Can Hermit Crabs Live Without Humidity?

According to Anthropod Structure & Development, land hermit crabs use modified gills for breathing.

When you think of gills, underwater creatures like fish come to mind – their gills allow them to breathe underwater. This isn’t true for hermit crabs living on land. 

If land hermits stay underwater for too long, they’ll drown. Also, hermit crabs’ gills can become damaged if they get too dry, which makes it impossible for them to breathe, resulting in suffocation.

How Long Can Hermit Crabs Go Without Humidity?

While there isn’t a specific length of time, hermit crabs will die without humidity. Once the humidity drops too low, hermit crabs experience difficulty breathing. 

Suppose you were in a situation where the oxygen level was dropping. You’d find yourself struggling to breathe. As the oxygen level continued to decline, you’d suffocate slowly.

The same thing happens with hermit crabs when the humidity becomes too low. When there’s no more humidity, the hermit crabs die.

can humidity be too high for hermit crabs?

Hermit Crab Humidity Requirements

Hermit crabs must be in an environment with a temperature range of 80 to 85 degrees Fahrenheit with an ideal humidity of 75% to 85%. The difficulty of maintaining the temperature and humidity levels depends on where you live and the season. 

For example, if you live in an area where humidity is often higher, maintaining the moisture in the hermit crab’s tank will be easier than living in a place where the humidity is naturally lower.

Whereas if you live in an area where winters get cold, and the air in the home is drier due to using a furnace for heat, you’ll have to work harder to raise the temperature and humidity in a hermit’s tank. 

Can Humidity Be Too High for Hermit Crabs?

Humidity levels above 85% won’t harm hermit crabs, but high humidity can cause excessive condensation in the tank, leading to mold and fungus growth.

Also, failing to clean a hermit crab’s tank regularly can cause fungus and mold to grow.

If you see any mold or fungus, you’ll need to remove the hermit crabs and thoroughly clean the tank, including the toys, plants, rocks, and whatever other items you have in there.

Never reuse bedding from a mold or fungus-infested cage. 

Mold spores can even sometimes begin growing on your hermit crabs. If this happens, give your hermit crabs a saltwater bath and a freshwater rinse. Let your crabs dry before putting them back in the tank.

How To Create Humidity for Hermit Crabs

You’ll need the proper equipment to create the optimal humidity level for hermit crabs. Here’s a list of essential items you’ll need for your tank:

  • Plastic or glass tank.
  • Tank lid.
  • Substrate.
  • Heat source.
  • Thermometer.
  • Hygrometer.
  • Water bowls.
  • Items for hiding.
  • Decorative items.

Plastic or Glass Tank

You’ll need an enclosed tank made of plastic or glass that’s big enough for the number of hermit crabs. Remember, you need 5 gallons of space for every two hermit crabs. So, if you have 4 hermit crabs, you’ll need at least a 10-gallon tank. 

Tank Lid

The tank lid is the tricky part. If you don’t use a cover at all or if you use a mesh one, you won’t be able to keep the humidity in the tank.

If you use an aquarium lid with openings for fish filters, you’ll need to cover some of those openings. The best thing to do is to use a piece of plexiglass as the lid and drill a few small holes to allow fresh air in but not let too much humidity escape. 

Substrate or Bedding

You’ll need a substance at the bottom of the tank, such as sand, moss, or cocofiber. Also, you can use a combination of substrates.

Hermit crabs like to burrow into the substrate to hide or when they’re molting. Moss, sand, and cocofiber will maintain the humidity in the tank, but there are also other options.

Heat Source

An under-tank heat pad or mat is the best heat source for a hermit crab tank. These heating pads create a consistent temperature in all areas of the tank.

As an alternative, you can use overhead heat lights or ceramic heat emitters, but these aren’t recommended as it’s hard to maintain a consistent temperature with them.

Never use heat rocks because they’re unsafe for hermit crabs. 

Thermometer and Hygrometer

You’ll need a thermometer to measure the temperature in the tank.

A digital hygrometer is a must, but hygrometers often need to be re-calibrated to work. So, if your hygrometer displays an unusual humidity level, ensure the hygrometer isn’t reading inaccurately. 

Water Bowls, Items for Hiding, and Decorative Items

You’ll need two water bowls – one for saltwater and one for fresh water. You’ll need items the hermit crabs can easily hide in or behind, such as large rocks, broken pot pieces, small tree limbs, etc.

Also, you’ll want some decorative items, such as plants and things the hermit crabs can climb on.

what humidity for hermit crabs?

How To Keep A Hermit Crab Tank Humid

Here are a few ways to increase and maintain the humidity of a hermit crab tank:

Hand Mister

You can spray the tank with unchlorinated fresh water using a hand mister. While this method works in a pinch, it’s not ideal because it only lasts a few hours.


As mentioned above, sand, moss, and cocofiber are the ideal substrate types for a hermit crab tank. Each of these substrates holds moisture well, which will help with keeping the tank humid.

However, sand and cocofiber can sometimes dry out, so check to ensure they’re moist. In addition to using moss for substrate, you can spread moss around the tank for the hermit crabs to play in. 

Tank Foggers And Humidifiers

You can buy foggers and humidifiers for tanks that keep moisture flowing through the tank’s air. You need to monitor them as sometimes they can cause flooding issues if too much water is distributed into the tank too quickly. 

Hermit crabs aren’t easy pets to look after. As long as you’re prepared to closely monitor the temperature and humidity in their tank and take care of their basic care needs, your hermit crabs have a good chance of living long and happy lives.