Ventilation and Air Exchange in a Rainforest Vivarium

Plants draw carbon dioxide from the air and release oxygen, while animals breathe in oxygen and exhale carbon dioxide. This means that it is theoretically possible to balance the plant and animal biomass in a vivarium carefully enough to keep it hermetically sealed.

The truth is that few keepers will find this to be realistic in practice.

Accordingly, you’ll need to ensure that the air in your vivarium is refreshed more-or-less constantly. This will ensure that all of the organisms in the habitat will remain healthy and thrive. It includes your pets, the plants and all of the microorganisms lurking in the substrate.

However, air exchange will also alter a few other characteristics of the habitat. You’ll need to keep these characteristics in mind when designing, constructing and maintaining the vivarium.

Providing Air Exchange for the Habitat

Because air is a gas, and gases diffuse and expand to fill the container they’re in, all you need to do to ensure air exchange is to place a hole in the vivarium. The gas molecules in the vivarium will slowly mix with those outside the vivarium and vice versa.

However, there are two primary considerations you must keep in mind when doing so:

  • Placing a hole (or holes) in your vivarium provides the inhabitants with a potential escape route.
  • The rate at which the air is exchanged with the air in the room will depend on the size of the hole.

So, you must provide a hole that is small enough to prevent your pets from escaping, yet large enough to allow enough air exchange to take place. These two solutions may seem to work in opposition. But it is actually fairly simple to provide a large hole for air exchange, while still preventing escapes. You must simply use aluminium or nylon screen to cover the hole(s).

Aluminum & Nylon Screens

Screen will provide plenty of open space for air to flow into and out of the habitat, while still preventing your pets from escaping. Screen is not always secure enough for very large or potentially dangerous species (such as venomous snakes). But it is usually adequate for the types of frogs, lizards, small snakes that are typically kept in rainforest vivaria.

Different types of enclosures incorporate different amounts of screened area. Most aquariums and commercially manufactured enclosures replace one of the glass, plastic or wooden sides with screen. But other enclosures – especially custom-built units – incorporate relatively little screen.

One full side of screen (whether the screened wall is placed on top of the enclosure or on one of the sides) will typically provide more than enough air exchange for most commonly kept pets. However, a few species – including, most notably, true chameleons – will require more air exchange than this.

In fact, one full side of screen will often provide too much air exchange for a rainforest vivarium.

But this brings up an important question:

Why would too much air exchange be a problem?

After all, animals living in the wild are surrounded by fresh air in all directions.

The answer lies in the way air exchange can alter the characteristics of the habitat – specifically as it relates to two different parameters.

Problems Caused by Excessive Air Exchange: Reduced Humidity and Lost Heat

Any time you allow the air inside your vivarium to mingle with the air outside the habitat, the enclosure will lose two things to the surrounding environment: water and heat.

Rainforests are humid places, just like vivariums that mimic them. Water from the water dish, daily mistings and substrate evaporates and mixes with the air, thereby raising the humidity. This is a good thing, as most rainforest-dwelling reptiles and amphibians have evolved to live in high-humidity environments.

However, because most homes have relatively dry air, air exchange between the vivarium and the surrounding room will result in decreased humidity inside the enclosure. This will become evident in a short time after maintaining the habitat. You’ll notice the water level in the dishes and reservoirs will fall and the substrate will dry out over time.

The more space for air exchange you provide, the quicker the habitat’s humidity level will fall. So, it is often necessary to reduce the amount of air exchange allowed or regularly add water to the habitat.

This will maintain a suitable amount of fresh air, without allowing the humidity to drop to inappropriate levels. In most cases, you’ll want to employ a combination of both approaches.

And just like the water in the habitat’s air will escape into the surrounding room, so will the heat you add to the habitat. Enclosures with large portions of screen will allow the warm air in the vivarium to flow out into the room. This means you’ll often need to adjust the amount of ventilation provided while simultaneously adjusting the amount of heat you add to the habitat.

Provide your pet with the proper conditions

Ultimately, you’ll have to tweak three different parameters to provide your pets with the proper conditions:

  1. Adjust the amount of heat provided, based on the desired humidity level and rate of air exchange,
  2. Adjust the rate at which you add water, based on the desired temperature and rate of air exchange,
  3. Adjust the amount of air exchange provided, based on the desired temperature and humidity level.

These parameters all influence each other, and “pushing” or “pulling” on any of the three will alter the other two.

Personally, I prefer to begin by providing the proper amount of heat to a habitat. I then tweak the amount of ventilation and water added to maintain appropriate conditions. I err on the side of too much ventilation, rather than too little, as I don’t mind adding more water to the habitat as necessary.

Using Fans in Rainforest Vivaria

In an effort to provide plenty of air exchange, some keepers like to incorporate small fans into the habitat design. Many keepers use computer fans when doing so, as they’re small, easy to wire up and affordable. However, any low-powered fan will work.

I don’t like to use fans, as I find that they don’t provide any particular value that couldn’t be attained by simply providing more space for air exchange. Instead of adding a fan, I’d just increase the screen-to-solid-wall ratio.

However, they may be helpful in some circumstances.

For example, enclosures that are built without very much screen may not provide enough air exchange. In such cases, a fan may help provide adequate fresh air for your pets and plants. Similarly, if you must use a high-powered heat source for some reason, a fan may help you maintain appropriate temperatures.

If you elect to incorporate a fan into your habitat, be sure that you place the fan outside the enclosure to keep your pets safe, and cover it with some type of grill, to prevent people from inadvertently sticking their fingers in the blades.

It may also be helpful to plug the fan into a timer. This will allow the humidity level in the habitat to rise while the fan is off and fall once it clicks on. This can even allow you to mimic the humidity cycles that typically occur in most natural habitats.

Common Problems Associated with Improper Ventilation

There isn’t a practical way for reptile and amphibian keepers to measure air exchange. You must monitor your pet, plants and overall habitat to ensure that you are providing an acceptable amount of ventilation.

This primarily means watching for problems that may arise due to insufficient or excessive ventilation. Some of the most common signs of problems include the following:

Plants Begin to Wilt

The plants living in habitats with too much air exchange may begin to wilt. This occurs due to dropping humidity levels, which accelerate the rate of transpiration (the process by which plants draw water from the soil or substrate and releases it into the air from small pores on the leaves).

Snakes and Lizards Experiencing Poor Sheds

Snakes and lizards living in habitats with excessive ventilation will often experience poor sheds. This occurs because the habitat humidity will drop in response to high levels of air exchange. For problem-free sheds, most rainforest-dwelling snakes require high humidity levels.

Reptiles and Amphibians Showing Signs of Dehydration

Reptiles and amphibians living in habitats with too much ventilation may exhibit signs of dehydration. This includes shriveled skin, sunken eyes and lethargy. They may also spend long periods of time in the water reservoir or damp hiding places. It is always important to address dehydration-related issues immediately. It is especially important to do so when keeping amphibians or very small reptiles.

Vivaria That Develop Bad Odors

Vivaria that do not have enough ventilation often develop bad odors. Many bad odors are associated with anaerobic bacteria, who thrive in oxygen-free environments. Providing more air flow will reduce vivarium odors by diluting the odor-causing molecules. It will also serve as a check on the development of some anaerobic bacteria.

Vivaria Coated in Mold

Habitats without sufficient ventilation may become coated in mold. Most fungi require high humidity to thrive, and they typically proliferate in habitats with damp and stagnant air. Molds (and other opportunistic microorganisms) may coat the sides of the habitat, the decorations or even the surfaces of the plants.

Animals Suffering From Respiratory Infections

Animals living in habitats that provide improper ventilation and humidity levels often suffer from respiratory infections. Respiratory infections can occur in pet reptiles and amphibians for a number of reasons, including exposure to infected animals and stress,. But improper ventilation or humidity can also cause such problems.


Condensation may indicate that the habitat lacks sufficient ventilation. Condensation on the sides of a habitat (particularly glass enclosures) signifies that the air is more-or-less saturated. This may be desirable in some cases, such as when maintaining rainforest-dwelling amphibians. But it may also indicate that the humidity level is too high and/or that the ventilation is insufficient.

At the end of the day, you’ll need to monitor the habitat closely and make adjustments based on the evidence available to provide the proper amount of air exchange with the surrounding environment. Accordingly, it is a good idea to avoid permanently restricting the airflow of a vivarium. Even if you achieve the perfect amount of airflow, the environmental conditions in your home may change over time. This will force you to make adjustments to the habitat.

Ben Team

Ben Team

Ben is a life-long environmental educator who writes about the natural world. He’s kept and bred a diverse array of reptiles and amphibians over the last three decades, but he’s always been particularly fond of snakes in the genus Morelia and monitor lizards. He lives in Atlanta, Georgia with his beautiful wife and spoiled-rotten Rottweiler.