Humidity is one of the most important factors for hermit crab success. It is vital to provide adequate humidity and heat to maintain the tropical climate they require.

Hermit crabs do not have lungs, and they do not have gills like fish, they have modified gills. These modified gills are not able to capture oxygen in low humidity environments. For the modified gills to function, they require constant humidity in the 80-100% range.

Hermit crabs require humidity at a constant 80-100%. This is one of the most important factors of hermit crab care. 

 

What is humidity?

Humidity is the measure of water vapour in the air.

How is it measured?

There are 3 main measures of humidity:

Absolute :Absolute humidity is the mass of water vapor in the air. It is often measured mass by volume; eg grams per cubic meter, ounces per cubic foot. It can be measured by dry air, or moist air.

Relative : Relative humidity measures the current humidity relative to the maximum humidity at the same temperature. This measure is expressed as a percentage from 0-100% * this is the measure most used for hermit crab keepers *

Specific :specific humidity is the ratio of water vapor to air for the total moist air mass .

What is a hygrometer?

A hygrometer is the instrument used to measure humidity.

Types of hygrometer:

1. Analogue – An analogue hygrometer has a dial and needle that indicates relative humidity. These can be as accurate as a digital hygrometer, however they take longer to register the change in humidity.
   

   

   

2. Digital- A digital hygrometer uses batteries, and it has a digital readout on the screen. Generally these will register changes in humidity almost instantly.
   

   

   

How to calibrate a hygrometer:

https://www.cigarsinternational.com/cigar-101/calibrate-a-hygrometer/1818029/

 

How is it increased?

Humidity can be increased by adding air stones to their water pools. More humidity can be added by renewing your pools with a larger model.

Sealing the top of the tank to prevent humidity escaping. A glass lid with gaps for air stone hose is a good way to ensure high humidity.

Ensure the substrate is evenly moist, but not wet. It should be sand castle consistency.

How is it decreased?

Make gaps in lid larger, but be sure that the crabs cant escape.

turn down the air stones in pools.