Crabitat: Humidity - Importance, Creating and Maintaining

This is where you discuss the conditions of your crabitat -- temperature, humidity, substrate, decorating, etc.
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Crabitat: Humidity - Importance, Creating and Maintaining

Post by HCADirectors » Wed Mar 13, 2013 2:07 pm

The humidity levels for hermit crabs should be kept higher than 70% at all times. Hermit crabs breathe using modified gills rather than lungs, so when their environment is too dry it can cause severe injury, and extended periods of low humidity can even lead to death. An ideal relative humidity range is between 75% and 85%. Humidity levels higher that 85% are safe for hermit crabs but can lead to unwanted condensation on the glass and increased mold growth.

Hygrometer (Humidity Gauge)

To monitor the humidity level in your crabitat, a hygrometer must be used at all times. Do not guess! Humans are extremely bad at judging humidity levels through touch alone and humidity levels that are too low can be deadly to your hermit crab. There are two types of hygrometers – analogue (has a dial) and digital. Most crabbers find that the analogue hygrometers sold for pet use are not accurate, and instead recommend the small digital dual hygrometer/thermometer unit that is sold at Walmart for about the same price.

Calibrating your hygrometer

Never assume that a new hygrometer is working properly. They are notorious for needing calibrated - tested and adjusted to make sure they are reading properly - even when brand new. If you suddenly discover that you are having problems maintaining humidity levels, it is a great idea to check that the hygrometer is still reading properly as they are known to fail without warning. Many times our members have driven themselves crazy trying to fix a humidity problem that did not exist, simply because their gauge stopped reading properly. To find out how to calibrate a hygrometer, please click here [Crabitat: Calibrating a Hygromter]

Humidity Gradients and Gauge Placement

Every enclosure is going to have some variation in humidity levels from side to side, front to back, and from to top to bottom. The warmer areas closest to your heat source will be drier, and the cooler areas farther away will have a higher humidity. The area right above the moist substrate will have a higher humidity level then up toward the top of the enclosure. Where you place your gauge or gauges is up to you, but you should consider putting it near to where your hermits spend the most time. A gradient (small variation) of humidity throughout the tank is recommended so long as it is within safe limits.

Increasing Humidity Levels

In some areas of the world, a high level of humidity is a daily occurrence and so it is not a challenge to maintain humidity in the hermit crab’s enclosure. For other areas, keeping humidity high levels can seem impossible - especially in winter with a furnace that dries out the air in your home. If you are having difficulty maintaining humidity, there are several things that can be done:

Hand Mister
The old stand-by - but it doesn’t work all that well. You may be able to boost humidity in the short term by spraying the tank down with dechlorinated fresh water, but it rarely lasts more than a few hours. (Never use saltwater for misting – the salt will stay in the environment until you change the substrate and wash all the items that have been sprayed, and high salt levels can cause exoskeleton damage during molts.) If you’re finding yourself misting more than once a day, try some of the other ideas farther down!

The first thing to look hard at is the lid on your enclosure. Screen lids will allow all the moisture that is in the tank to escape, so it need to be covered with plastic wrap, packing tape (sticky side facing out!) or panels of plexiglass or glass. Glass or aquarium hoods may allow too much humidity to escape through the gaps that are for use with fish filters, and these too can be covered using the above methods. There should still be some fresh air flowing through the lid, so covering it completely is not recommended unless you are also using a humidifier or bubbler. You can cut or drill vents to allow fresh air in, and this will also allow you to control how much humidity is being held inside the tank.

Never soak your substrate to raise humidity levels! This can cause catastrophic flooding at the bottom of the tank which can drown molting hermits and cause dangerous bacterial growth. However, you should check to make sure that your substrate is staying at sand-castle consistency, as once the substrate dries out so does the air above it. Substrate will dry out faster closer to whatever heat source you have chosen to use. Organic based substrates like cocofiber can help to boost humidity levels. These substrates release moisture fairly consistently, although they can dry out quickly. Using a mixture of cocofiber and sand can help to stabilize humidity and the more cocofiber that is used, the more of a boost to the humidity. More information about crab-safe substrates can be found here [Crabitat: Substrate & Moss]

Water Dishes and Bubblers:
Try to use bowls or pools that are wide, as the increased surface area will create more humidity. Water dishes may be placed near your UTH or beneath your overhead light to produce additional humidity though evaporation. Adding a bubbler – a fish air pump with an air stone – that sits in the water dishes can also boost humidity levels. However, if the pump is too powerful, the air outside the tank is too dry, or if the pools are too shallow it may have the reverse effect and cause the humidity to drop even further.

Natural moss
Not only does it help to boost humidity, but crabs also love it! Placing moss anywhere in your tank and keeping it damp will raise the humidity. Many crabbers choose to create “moss pits” by using shower caddies and other non-molding containers and filling them with moist moss. The hermits will hang out in them, and there’s an added bonus of it being easy to moisten. However, moss can be added to the substrate or piled in corners, too. Make sure to use reptile moss from the pet store or other mosses that are safe for use with live animals. Mosses found at the craft store are often sprayed with pesticides to keep them bug-free, and this can be harmful to hermit crabs. There is a guide to buying and using moss located here. More information about using moss in a crabitat can be found here More information about crab-safe substrates can be found here: [Crabitat: Substrate & Moss]

Foggers & Humidifiers
The commercially available versions of these use electricity to evaporate water from reservoir tanks and pump the moisture-rich air through tubes into your crabitat. There are many brands and styles available, but not all are created equal so make sure to research before investing in one. They will certainly do the job of raising humidity levels! It’s important to watch how much water it’s using as flooding has occurred due to it adding too much water into the crabitat too quickly. DIY versions can also work well - there is a guide to how to build one using a jar, an air pump, and airline tubing located here: [Bundy's DIY Humidifier]

These are dangerous to use with hermit crabs. The water is immediately absorbed by the substrate which means it is not going to give much of a boost to the humidity in the air. It is also extremely easy to add too much water and flood the tank, which can kill any molting crabs.