Welcome to The Crabstreet Journal

Login or Signup to meet new friends, find out what's going on, and connect with others on the site.

Sign Up Now

Registering for this site is easy. Just fill in the fields on the registration page and we'll get a new account set up for you in no time.

Forgot Your Password?

A new password will be e-mailed to you.

Member Login

You are browsing the archive for humidity.

Profile photo of Stacy

by Stacy

Calibrating your Humidity Gauge

February 21, 2013 in Crabitat

written by Rai Ahmes

Relative humidity (RH) is measured as a percentage–absolute and specific humidity are NOT. If it reads in % it’s a relative gauge. RH gauges are fairly inexpensive and commonly available. Gauges measuring absolute or specific humidity are hard to find and expensive; they also read in either g/kg or g/cubic meter (or the non-metric equivalent) not %. “Actual humidity” and “exact humidity” are not measurements.

Dial RH gauges are rarely calibrated properly by the time they reach your home. This is NOT the fault of the manufacturer. It is simply the way it is with this type of hygrometer whether it’s for your tank or for your house. This probably accounts for the wide variation of humidity levels that have been recommended. You can do something about this though :)

Calibrating your hygrometer:
First check to see if your hygrometer can be adjusted. Look at the back to see if the small center post has a slot for a small screwdriver. If it does you’ll need to have a screwdriver ready to make any adjustments as soon as you open the jar. If it doesn’t, don’t worry, this procedure will still allow you to use your hygrometer more effectively.

Half-fill a shot-glass or other small dish with table salt and add enough water to wet the salt completely but not dissolve it–it should be like wet sand. Put the shot-glass and hygrometer in a wide-mouth jar, and seal it airtight. After six hours (or more), the humidity in the jar is 75%. The hygrometer should read somewhere around 75%. If it does not, take the screwdriver and turn the screw on the back of the hygrometer until the meter reads 75%.

If your hygrometer is non-adjustable and reads other than 75% in the jar, you must correct all subsequent readings by this difference. Example: if the hygrometer reads 67% in the jar, it is reading 8% low. Thus, it will always read 8% less than the actual RH. Using this example if you wanted the humidity to be 60-70% then the reading on your hygrometer would have to be 52-62%.

Dial RH gauges can be off by 20% or more! They are also usually only accurate to +/- 5% and often take up to 2 hours to finish stabilizing to a new reading if the humidity changes. Please remember that it is simply the nature of the beast and NOT necessarily poor quality or manufacturing. The spring mechanism is delicate and goes through a lot (shipping, etc) before reaching your home.

Profile photo of Stacy

by Stacy

FAQ How do I create and maintain humidity in my crabitat?

October 16, 2012 in FAQ

Answered by Stacy Griffith
The first step to creating and maintaining humidity in your tank, is a good lid. A screen lid alone is not sufficient. A glass/plexiglass/lexan lid, cut to fit is the best option. In the short term, you can use plastic wrap over the screen lid. A small opening should be left for air exchange. The size of the opening may have to be adjusted until you find the right spot to maintain your humidity. Plexiglass/lexan can be purchased at most hardware stores and be cut to size for free.

Soaking your substrate is not the way to raise humidity. SLIGHTLY moistening the substrate above the UTH is okay.

Water Dishes:

Your tank should have two types of water bowls, salt and fresh. Use bowls that are wide and shallow. This increased surface area will create more humidity. Water dishes may be placed slightly over your UTH (under the tank heater) or beneath your overhead light to produce additional humidity.

Natural moss:

Crabs love moss! Placing moss anywhere in your tank and keeping it damp will raise your humidity. Replace as needed. You can buy moss at the pet store in bags or compressed bricks. Look for Hiawatha or sheet moss, terrarium or frog moss, natural and undyed.

What Moss is Safe?
Is Beaked moss safe?
Is Sphagnum moss safe
Is Cypress safe?
Don’t Forget the Moss


Repti foggers can be placed in the tank to create humidity as well. They cost around $30.00 and can be purchased at your pet store. You can make your own with the directions here: Homemade Humidifier

Spidtat/Travis’ review of his Tropicair Reptile Humidifier


Sponges were once considered a staple in the hermit crab tank but there are better solutions to the humidity issue. Sponges placed in the fresh water will raise humidity. Sponges should be changed out daily, sterilized and replaced with already sterilized sponges. Sponges placed in the salt water will become nasty fast. Due to the upkeep of sponges it’s easier to go with moss.

If you have just discovered that your crabs need humidity and you are not able to fix the problem immediately you can place a wet towel over the tank. The towel must be kept wet and this is not a long term solution. You can also mist the tank with dechlorinated water. This is not a long term solution either as the humidity will fluctuate too much between mistings to be suitable.

Originally posted at All Things Crabby The Hermit Crab Care Blog

Profile photo of Stacy

by Stacy

Understanding Humidity in the Crabitat

September 25, 2012 in Caresheets

Originally written by Vanessa Pike-Russell-Updated by Stacy Griffith

What is Humidity?

Humidity is a measure of the amount of water vapor in the air. It can be expressed in several ways.

“Specific humidity” is the mass of water vapor per unit mass of combined dry air and water vapor, generally expressed in grams per kilogram. The specific humidity of an air parcel does not change with temperature.

“Absolute humidity” is the density of water vapor, expressed as grams per cubic meter of air.

“Relative humidity” is discussed below. Related terms are “saturation,” which describes the condition where water vapor is at a maximum concentration for the air temperature (warm air can hold more moisture than cold);

“dew point temperature” the temperature at which saturation occurs if air is cooled at constant pressure without addition or removal of water vapor; and

“vapor pressure,” which in meteorology is that part of the total atmospheric pressure due to water vapor content.

Reference: Arctic Climatography and Meteorology

What is the Ideal Humidity Range?

Humidity should be between 50-60% for Actual and around 70-80% relative humidity.

How can I measure humidity within my Crabitat?

You will need to buy a humidity gauge, also known as a hygrometer.
There are many kinds, some of the more popular are shown below.


The ESU Reptile Humidity & Temperature Gauge allows you to accurately monitor humidity levels from 0-100% and temperature levels from 60o to 120oF (15o to 48oC) in your reptile’s habitat.


Fluker s round thermometer is calibrated to enable you to effectively monitor an Environmental Temperature Range (ETR) within your pet s enclosure to promote good health and longevity

Fluker s relative humidity hygrometer allows to establish and maintain a consistent level of humidity within your pet s enclosure, creating a safe and comfortable environment.

Fluker's digital humidity gauge HUMIDITY & TEMPERATURE GAUGE (DIGITAL)

The digital thermometer/hygrometer comes equipped with a “min/max” button that displays the minimum and maximum levels your enclosure has experienced. This is important for measuring severe, sometimes fatal fluctuations in the temperature and humidity level. The product also has a (C) Centigrade and (F) Fahrenheit temperature display choice, depending on the owner’s preference.

Hermies and Herps Digital Combo HUMIDITY & TEMPERATURE GAUGE (DIGITAL)

The digital thermometer/hygrometer comes equipped with a “min/max” button that displays the minimum and maximum levels your enclosure has experienced. This is important for measuring severe, sometimes fatal fluctuations in the temperature and humidity level. The product also has a (C) Centigrade and (F) Fahrenheit temperature display choice, depending on the owner’s preference. Comes with a probe to test at substrate level, or for hot spots. Made in Asia.


The T-Rex Habitat Thermometer is compact and mounts naturally at any desired location inside the habitat, giving accurate readings in a wide range from 60 F to 120 F. For best results, use two: one in the hottest area of the enclosure, the “baking zone” and one in the coolest corner.


Allows for precise monitoring of both the temperature and humidity of your terrarium from one unit!
Thermometer scale: 20 to 140 F (-6 to 60 C).
Humidity scale: 0 to 100%.

Digital Gauge with Alert Accurate Measurement of Water Temperature with Low/High Temperature Alert Preprogrammed for Tropical Fish & Clock for your convenience.

  • Digital Thermometer with probe
  • 3ft (with all plastic probe & suction cup cord) allows for accurate measurement of water temperature
  • Low/High temperature alert plus on/off button
  • Fahrenheit Display (75-82 degree F)
  • Dimension (L x H): 2-2/3″ x 1-2/3″
Profile photo of Stacy

by Stacy

Misting your Hermit Crab

September 25, 2012 in Caresheets

Misting Your Hermit Crab

Misting is commonly considered to be unnecessary and potentially stressful by most crabbers. If your tank humidity is at a recommended level and you offer fresh and salt water pools deep enough for your crabs to wade in, there is no benefit in regular misting. If you choose to take your hermit crab out of its tank for playtime or exercise, it is a good idea to mist the gills.

Misting is a method of keeping your hermit crabs moist in between baths.

As in the case of bathing, only use water that is free of chlorine and chloramine and if the water in your local water is deemed as not suitable for keeping fish in (eg. heavy metals, chlorine or chloramines) then it is not suitable for your hermit crabs.

Misting should never be done inside the crabarium because moist substrate leads to the growth of bacteria which is often fatal to hermit crabs.

A gentle misting is also a way to ease out a shy hermit crab. It has been suggesedt a light misting to coax a shy hermit crab out to play.

If the temperature rises and you are worried your hermit crabs will dry out, give them a light misting outside the crabarium and wait until they dry before putting them back inside the tank.

Misting once every few days or so is beneficial to your crab but not compulsory. Use common sense and provide the extra moisture when your crab needs it.

ChatClick here to chat!+
%d bloggers like this: