When and How to Use Mist and Rain Systems

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Misting and Fogging Systems are Often Misused —

There is a place for overhead precipitation systems in herpetoculture – fog, rain or mist – but they are not common. The vast majority of keepers dont need them, and in fact they are very often over used by keepers who have installed them. They should not be a part of a naturalistic or bioactive build unless a species specific needs are being addressed – this is uncommon – or unless they are simply being used to re-wet substrate.

The recipe for bioactive or naturalistic set-ups is typically: Misting system, drainage layer, fancy substrate. But in 95% of bioactive vivariums we can leave all of these elements out. In fact we would do better to leave all of them out.

Misting systems got started when herpetoculturists made the mistaken assumptions that 1.) Tropical species, especially tropical frogs, need very high and constant humidities, and that 2.) the best way to deliver that high, constant humidity was from above via mist. These mistaken assumptions led to the need for special substrates and drainage layers – both needless complexities, and needless expenses and both potentially quite damaging).

For most of our vivariums humidity should come from the substrate. (See: The Humidity Mystery, Managing Substrate Moisture, and Why Drainage Layers Suck). Overhead misting causes quick spikes followed by quick declines – both unnatural and unhelpful. Many keepers resort to closing down ventilation in an effort to keep the humid air around a little longer – compounding one mistake with another.

In fact the entire paradigm of misting system, special substrate, drainage layer is little more than a series of mistakes built on false assumptions about the natural history of the species being kept.

In nature, our frogs, snakes and other species access humidity by going to ground, not by basking in humid air (some exceptions obviously). My dart frogs immediately establish humid refuges under the curls of dried leaves in their vivariums for example. And without any over head mist the humidity in these refuges will remain very high for many days to even weeks if substrate moisture is monitored. (See: Managing Substrate Moisture).

Ball pythons access high humidity by retreating to burrows in the ground during the dry season. Keepers can emulate these natural conditions by using the right substrate (See: Comparing Bioactive Substrates) and learning to monitor the substrate moisture.

That doesnt mean we should never incorporate overhead watering systems. It does mean we should do so only if we are sure the benefits out weigh the costs. And if mismanaged, the cost can be high!

There are two times when mist or rain systems can be useful. One is when you are using them to simply re-wet the substrate. Deep potting mix substrates (See: The Great Substrate Debate) needs to be recharged every week, every couple weeks, or every month or two depending on the substrate depth, cage ventilation, radiation, etc. I have built these re-wetting systems out of 1/2 inch PVC pipe with very small holes drilled into them and then attached via plastic tubing to an inexpensive water pump placed in a 5 gallon bucket filled with warm tap water.

If you have big cages, or lots of cages, its easier to re-wet substrate with a built in system like this than with a hand mister or hauling jugs of water. This simple system can be connected to the residence’s plumbing system too via a garden hose, further simplifying it.

A note of advice about using such a system. When I posted video of one of my re-wetting systems in action I received a number of comments that I was over-watering. The viewers watched as about 5 gallons of water were run thru the system, which looked to them to be much too much. But in fact I ran 15 gallons of water thru the PVC piping in order to re-wet the substrate in this 8×2 foot cage. It is as easy to underwater a substrate as it is to over water! If you are using good potting mix substrate and not, for example top soil (See: What’s Wrong With Top Soil) or a coconut based substrate (See: What Wrong with Coconut Husk Substrate?), the water will spread through the substrate and create a uniformly, slightly damp (never wet) substrate. But if you dig down into the substrate the following day (give it 24 hours to permeate the dry areas) and it has not evenly wet all the substrate to the bottom, you know you need to add more. If the substrate is actually wet, instead of just damp, you know you have over watered. Expect gnats until you get things dried out a bit!

The second situation you will actually want a misting or rain system is if you are designing for a species that is highly adapted to rain. There are very few of these species! These are mostly species that are highly arboreal in nature and descend to the ground only when they have to. These snakes and lizards and frogs drink or replenish water stores from water droplets or water pools collected in bromeliads and similar plants. Some are actually reluctant to drink from standing water, some apparently can’t or dont. See for example, https://reptilesmagazine.com/keeping-the-java-hump-headed-lizard/

An example are the green tree pythons and emerald tree boas that I keep in cages with warm water rain systems and no substrate at all. These species are stimulated to pass waste when it rains. When they dont have access to rain they can become constipated and require a vets intervention. Watching my snakes react to the warm rain makes me believe a rain system is an important aspect of their care. Note too Im saying “rain” not “mist”. The actual rain drops are more natural and seem to elicit a natural response in these animals.

But because it is rain and not mist or fog, the cages have to be plumbed much as a household shower is plumbed. Excess water runs out of the cage thru a drain and carried to the room drain through PVC drain pipe. Each cage may receive 10 or more gallons of water over a 15 to 20 minute rain a few times per week. My system is connected to a timer so the snake’s showers can happen at night when their warm water use doesn’t conflict with the families!

I will soon update these pages with photos and videos of how the rain and re-wetting systems Ive built are designed.

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Published by Joe

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