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When one begins growing more and more carnivorous plants, there will eventually be a point at which you will want to grow plants that just aren’t suitable to be grown outside or in your house due to special lighting, humidity, or temperature requirements. When this situation arises a very affordable and easy solution is to set up a carnivorous plant terrarium.
When setting up a terrarium for your carnivorous plants, it is typically not best to put soil directly into a tank and plant your plants into it like many terrariums that are sold for desktops. Typically the best way to grow a number of carnivorous plants in a terrarium setting is to just put individually potted plants into a tank, and then water them individually from above or by using the tray method (depending upon the plants you are growing). Using this method you can control the environment of your plants but can easily remove them from the terrarium for cleaning, or dormancy requirements.

This type of terrarium is referred to as a greenhouse style terrarium. A greenhouse terrarium is set up to be just that, a miniature greenhouse, and can support nearly any type of carnivorous plants depending upon their size, light, humidity, water, and temperature requirements. Some of the very rewarding carnivorous plants that thrive in greenhouses such as Nepenthes, Heliamphora, Cephalotus, can be grown by anyone in the right type of greenhouse style terrarium.

When setting up a greenhouse terrarium for your carnivorous plants, the first thing to consider is what type of carnivorous plants you are going to be growing in it. If you plan on growing only a large collection of rosetted sundews, you would construct a very different terrarium as compared to what would be needed for a collection of Nepenthes. In any case, the first thing you need to select for your terrarium is what type of tank or enclosure you are going to grow your plants in. The standard solution is to use some type of aquarium. Another possibility that can be cheaper when you need a large amount of growing space, is to construct the floor, sides, and back of your terrarium from plywood, and use a sheet of Plexiglas for the front.

The biggest advantage that a real greenhouse has over a greenhouse terrarium is natural sunlight. The reason why carnivorous plants do so well under natural sunlight is not because sunlight contains special photons that artificial light doesn’t, but because sunlight has so many more photons. The key to good artificial lighting is intensity (brightness). In most cases fluorescent lights will be fine for your carnivorous plants. The more fluorescent tubes you have, and the closer to your plants they sit, the better. If you are building a taller terrarium, you will need to increase the intensity of your lightning beyond just a few fluorescent bulbs. One solution is to cast light into your tank from not only the top, but also the sides. This approach can make it possible to grow taller plants such as Nepenthes and Sarracenia.

Another approach is to use other type of lights such as halide bulbs or sodium incandescent bulbs. These more expensive lights are significantly more intense than fluorescent bulbs and are ideal for larger terrariums in which taller plants will be grown. Another way to increase the intensity of the light reaching your plants it too prevent more of it from being lost through the sides of your tank. It an aquarium, attach mirrors or silvery reflective to the back and sides of the tank. This will bounce light back onto your plants that would have been lost through the glass of your tank. In a wooden framed terrarium, painting the insides of the tank with a bright white latex paint will not only help reflex light back onto your plants, but it will also help keep the tank more humid, by not allowing the moisture to seep through the wooden back and sides. Also in a wooden tank, mirrors or Mylar can be attached on the inside for a stronger reflective effect. Also, in either case, if your terrarium is somewhere that is not continuously viewed, covering the front with a mirror that can be removed for viewing in addition to the sides and back will create a very bright reflective effect that can really improve the coloration of your plants.

When watering your plants in a terrarium, remember to follow the basic guidelines for watering the species you are growing. For plants that do well on a tray system, pots could be placed individually in water trays or grouped together by their specific needs. Or if all plants on the tray system like similar wetness conditions you could use the entire bottom of the terrarium as a water tray. In either case plants that need adequate drainage should be placed on pedestals so that they are lifted above the water level. This is advisable even if other plants are contained in separate trays. This way water will not pool around the bottom of the pots after watering and reduce drainage. When using an aquarium as your tank, there is no special attention that needs to be paid to waterproofing. In a wooden framed tank, one approach is to staple a rubber or plastic liner the sides near the bottom of the tank. Another possibility would be a large shallow tray that covers the entire bottom of the tank and catch any draining water. Once again, make sure that you only use water that is low in salts and minerals such as distilled water or rainwater.

Humidity is the main reason why many carnivorous plants need to be grown in a terrarium in the first place. Carnivorous plants generally like a high humidity. In a terrarium it is generally not too hard to maintain high humidity levels. If there are water trays in your terrarium, the evaporating water from these trays will help maintain a high humidity. In addition to these evaporative effects, spraying a terrarium with a garden spray bottle full of distilled water will quickly raise the humidity of the tank. Another possibility for humidifying a terrarium is to use a small device commonly used in raising reptiles and amphibians. The device is a small disk that is submerged in a bowl of water and creates a thick fog of water vapor by emitting an ultrasonic tone. The fog looks like the fog from dry ice but is simply pure vaporized water. These devices can dramatically increase the humidity of a tank.
The temperature of your terrarium can be one of the trickier elements to control.

Fluorescent lights do not emit a lot of heat but a lot of them can contribute to warming a tank. Incandescent light do generate a lot of heat and are generally not used in terrariums because they will overheat your tank. Of course if your tank needs to be heated then low wattage incandescent bulbs may help. Other ways to heat a terrarium are heat pads and water heaters. Heat pads cab be placed under the tank and will generate heat. Water heaters can be submerged in a jar of water. They will heat the water and this hot water will heat the tank. Incandescent heating sources will likely have an effect of lowering the humidity of your tank, while water heaters will increase evaporation and increase the humidity of your tank. Cooling a tank is generally a more difficult task than heating a tank. The first step is to make sure that your terrarium is not in a room or location that is hotter than the tank needs to be. It is very difficult to make a tank cooler inside than the room outside. If the terrarium is cool outside then the easiest way to cool the inside is to create a greater air current into the tank from the outside. Also, be sure to try and cut down on devices that create extra heat (such as incandescent lights). For certain plants such as the highland Nepenthes, you will want the tank to drop in temperature at night, and rise during the day. In a cooler room this can usually be accomplished through the use of a heat source (or possible the light source will be enough) during the day, and a cooling fan inside the tank at night as well as a misting with a spray bottle at night.