Increasing Humidity in Your Tank
R. D. and Patti Bartlett
Before discussing ways to increase (and decrease) cage humidity, you will first need to measure it. Without measurement, you are only estimating what you think is going on. Purchase a hygrometer designed for use in reptile and amphibian caging, and put one hygrometer per cage, where you can easily read it. Put an index card and a pencil near the cage, so you can actually record humidity levels, both in the morning and in the evening. Now, when you try to increase the humidity in your cages, you'll know what works and what doesn't.
There are some very simple and easy ways to increase cage humidity. Plants, especially those with lots of leaves, will help. You can mist the cage contents twice daily, using a spray bottle, the type that are sold in most drug and variety stores and in most pet stores. Your animals may drink the spray droplets, and the humidity level in the cage is increased temporarily. Because the amount of water added to the cage is very limited, you usually don't need to worry about sodden substrate.
Another method is to add a larger, saucer-like water dish. The increased surface area means that more water will evaporate; the shallow depth is a precaution against your animal drowning. If an under tank heating pad is used under the water bowl, the humidity will increase even more dramatically (but be certain the water doesn't evaporate out of the bowl).
Depending on what you're keeping, you may be able to increase humidity in a cage by restricting humidity loss through the cage's screen top. Lay a piece of fine screening, such as a piece of window screen or mesh fabric, over the top of the cage. But not all animals react well to this decreased air circulation. Some, like chameleons, need a lot of air exchange. If you're working with chameleons, and they aren't in a wall-less cage like their own 12-foot ficus tree or in a mesh cage, consider angling the breeze of a small fan across the top of their terrarium. Chameleons don't do well in stagnant air.
If you're dealing with desert creatures like Namib geckos that require a very specific microenvironment that's damp but cannot tolerate an all-damp cage, you can add moisture to the bottom layer of substrate. You'll use what's called a standpipe, a piece of PVC or three-quarter aquarium tubing, equal in length to the depth of the substrate plus a few inches more.
Push the piping/tubing down through the sand in one corner until the bottom of the tube is just above the terrarium flooring. Pour a little water into the standpipe. For a 20-gallon terrarium, a half-cup of water may be all you need to moisten the bottom layer of sand in the corner of the tank.
Sometimes you may want to increase humidity in the cage and water your animals at the same time. The drip bucket is just a bucket with a hole in it, placed on the top of your cage. Once the drip hole is made and the bucket partially filled with water and placed on top of the cage, the water drips through the screen top of the cage into a shallow dish inside the cage. Make certain the dish is large enough to hold all of the water from the drip bucket. Empty the dish each evening, and in the morning you re-fill the bucket with fresh water.
When you first bring home imported animals, they may need more water than your hand-held mister or drip bucket can provide. These creatures will often need rehydration. These animals may have been kept in crowded holding facilities for several weeks before shipment to a stateside wholesaler. Many are too stressed-out to drink water from a dish, even when (or if) it has been offered. Animals especially in need of rehydration are the tropical species, those that generally originate in areas of high humidity, and those from seasonally wet/dry areas.
The more sophisticated rehydration systems are better described as rain chambers. Some types are separate cages, rather like a visit to a misty-cool spa. Some types are set up as part of the your regular caging, but care must be taken to ensure that the substrate doesn't get soggy and become fouled. Obviously, rain chambers are for both temporary and long-term use, depending on what you're keeping.
There are commercially available misting systems that use a water source, misting nozzles and in some cases, ultrasound, to produce a very fine water mist that drifts across the terrarium like a miniature cloud before settling out of the air. Depending on the system, expect to spend about $300 for a pump, the tubing, the nozzles and the timer. You just suspend the piping over the top of the cage, hook it up to the pump and timer and the water source, set the timer, and you're done.
If you need something now and sizeable expenditures are not part of your plans, you can still set up a rain chamber. One type uses a wire mesh cage set over a utility sink or in your shower. A shower head on a length of flexible piping – the kind you buy for yourself at a home supply store-runs from the faucet to the top of the wire mesh cage. Once you've adjusted the water temperature from the spigot to a range of 73 to 78 degrees Fahrenheit, you can affix the shower head onto the top of the wire mesh cage and let the fine spray run through the cage and out into the sink below. Do not leave home while this is running. You'll be amazed how readily a sink can become plugged, while the water from the faucet runs on and on.
Another system uses the same approach, but rather than a shower head, it uses a piece of PVC piping the length of the cage. The piping is drilled along its length with three rows of holes and is capped on the far end, creating what you might term a shower wand. The other end is connected with flexible tubing (either from your hardware store or your aquarium store) that has hose fittings on both ends. Attach the flexible hose to the faucet, turn on the water, and check the water temperature before putting the wand atop the wire mesh caging. Let the water run for an hour or so.
For an animal that's just dehydrated and doesn't require a rainforest environment with periodic misting, two or three hour-long sessions in the rain chamber may be all it takes to be rehydrated. The sessions can be repeated after a wait of three to twelve hours, but make certain the animal is in a temperature-controlled environment between hydration sessions. You'll be able to tell if this method of rehydration is working after the first session - your animals should look more alert and a little less thin or shriveled. After a few sessions, your animal can then go into a conventional caging/watering system (but keep an eye on it to make sure it's drinking water and feeding).
Increasing and measuring the humidity on your cages isn't a lot of extra work. It just means you need to set up a system that will work for both your animals and for you.