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Building and using a terrarium
One of the questions I get the most often is 'How do I build a terrarium for growing carnivorous plants?'. Good question. A terrarium set-up for cp's can be as simple or complex as you want it to be. This document will, hopefully, cover some of the aspects of all of these, and allow you to decide what to build for your puposes.
What is a terrarium?
Essentially, a terrarium is a contained system, much like an aquarium, except without all the water. Most people use old aquariums covered with a sheet of glass and use fluorescent fixtures over this. You can then put your plants in pots in the bottom, or cover the bottom with suitable substrate and let the plants fight for space amongst themselves!
The main advantage of a terrarium for cp's is that a high humidity and relatively constant environmental parameters can be maintained at all times. If you live in a dry climate, you may have little choice but to grow your plants in terrariums. If maintained properly, you don't have to worry about pests and diseases (except fungus), or at least less than plants grown outside.
The main disadvantage with terrariums is that the plants grown under them are 'soft'. With high humidity, the plant can put more energy into growth, and less into structure and protective mechanisms. When exposed to lower humidity, plants grown in soft conditions often wilt. Another disadvantage that I have found is that no matter what type of lighting is used, it can never beat natural sunlight.
How do I build a terrarium?
Ok, first you're going to need a few supplies. The rule of thumb is, decide on the size aquarium you think you'll need, and then double it. This allows for growth of plants and growth of collections! Trust me on this point. I started out with a single 5 gallon aquarium converted to a terrarium under two, two foot fluorescent fixtures. I have now expanded to a dual shelving system with three 10 gallon, three 5 gallon, one 15, one 20, and one 2 gallon terrariums, plus a total of four 4-foot fluorescent lighting fixtures. This doesn't include the plants I've got outside in the greenhouse and the yard. And yes, I'm running out of room again! Enough said, buy a larger terrarium.
The height of the terrarium should, preferably, be low. Tall growing plants, such as Sarracenia, don't do well indoor under light, as it's difficult to provide enough light for them. It's much better to stick to smaller plants such as the sundews, pings, and utrics. One of the big favourites of terrariums are the Nepenthes. Most do well, even under lower light, and they love the humidity!
The next thing you'll need is a cover of some sort. You can get glass cut to fit the top of the terrarium, or, in a fix, you can use plastic wrap. If you use glass, it's a good idea to use something that is relatively thick or tempered. This way it will withstand having objects dropped on it, or being dropped. This happens more often than you may think (wet hands, full of dripping pots of wet peat moss, and plants...).
Now you have the basic ingredients. What's next? Lights! This is a huge topic in itself. If you want really really detailed information, I'd suggest checking out The Krib, a site that deals with growing aquatic plants. I'm part of the aquatic plant group in Vancouver, and these people really know their lighting.
Having said that, probably the best lighting from the myriad available on the market is fluorescent. It may not be as efficient as metal halides, but it is way cheaper, both in initial costs and running costs. Some may argue that one metal halide is equal to many fluorescent, etc., but I find that with smaller terrariums, 200 watts of intense light isn't really necessary. If you buy a four foot tank, four foot light fixtures will do. They're sold either as shoplights, which are pre-wired so you just plug them in, or industrial fixtures, which you have to wire up yourself. If you choose to wire it up yourself, please make sure you know what you're doing before you electrocute yourself or burn down your home! One note before I move on. If you've decided on a larger terrarium and you do want metal halides (yes, they work very well in larger set-ups), there are a couple of sources that are cheaper than purchasing them through your hydroponics store. The first is Home Depot. These guys have a lot of stuff for cheap prices, including ballasts and lights for metal halides. The second is your local police station. Metal halides are the choice lights for marijuana growers. When they get confiscated, the police eventually auction them off at dirt cheap prices, like 1/10th the retail price or less. Ask them when they're going to have the next auction and if they have any lights available. However, be prepared for them to come knocking on your door, especially if you buy in large quantities, as the pot growers go out to these auctions too!
What kind of lights should I use?
Yes, saying fluorescent fixtures isn't quite enough, is it? Again, there's a wide variety of light bulbs out there, all with special features, special wavelengths, and so on. Basically, plants need light in the blue and red spectrum of visible light. 'Huh?' you say? Ok, white light (the light that comes from the sun) is actually composed of many different colours or wavelengths (a relative measure of their energy). When these wavelengths hit the plant, the plant tissues trap some of the energy. One of the laws of physics is that energy cannot be destroyed, only transformed or transferred into other forms. So, this energy the plant traps ends up stimulating photosynthesis and helping the plant grow. All you need to know, is that there is a wide spectrum of colours in sunlight, which include red, orange, yellow, green, blue, indigo, and violet.
Plants need light in the blue spectrum to stimulate growth, while they need light in the red spectrum to help stimulate flowering. Ultraviolet light (light at lower wavelengths than violet and invisible to our eyes) helps produce the reddish colouration in plants. Plants appear green not because they absorb that wavelength, but because they reflect it from their leaf surface.
Get to the lighting already!
Sorry about that. I'll try to contain myself. The lights you choose should have a balance between red and blue (that's the problem with incandescents, too much red light and heat is produced). No need to buy the really expensive growlights, cool white bulbs ($1 each or less) are sufficient. The growlights do seem to promote the reddish colouration, but I haven't found they're overly fantastic.
The other thing you'll need is a timer. This turns the lights on and off automatically for you. Set the timer to the natural daylight rhythm, which is approximately 8 hours of light in winter to 14 hours in the summer, all depending on your latitude.
What do I put in this terrarium?
Well, you have to decide whether or not you want a classic terrarium, or one with individual pots. I'll give a summary of each, and let you decide.
Individual pots
With this type of terrarium, each plant has its own pot and sits in its own saucer (or shares a larger saucer with another plant that shares the same watering requirements). The advantages to this are that a wide variety of plants can be grown that have different watering and soil requirements. If a plant becomes diseased, or if you want to take it out to propagate it, show it off, or any other reason, it's a very simple matter. The main disadvantages are that you have to water each individual plant and it doesn't look overly natural.
Traditional planting
This is one in which you place a substrate on the bottom and put the plants right in this. The substrate should consist of some charcoal on the bottom covered with the preferred cp mix. The main advantages to this type of terrarium are that it looks quite natural, when done correctly, and watering is simple. The disadvantages however, are many. You can only grow cp's that share the same soil and watering requirements together. If one gets a disease, the rest are likely to get it too. It's difficult to pull out an individual plant. Some plants, through seed or root runners, will eventually take over the terrarium and smother out the weaker plants.
You've been warned! Take your choice.
Set-up
So, now you have all the components, where to set it up? Best not to place it where the terrarium gets direct sun. This can cook the plants in a short amount of time. Not the best idea! Place it preferably at eye level, so you can admire the plants. Remember to keep the glass cover slightly offset. This will help prevent the spread of fungus. However, if you're growing Neps, you may want to keep it completely covered, as they seem to be resistant to fungus, and love the high humidity.
Maintenance
Not much maintenance is needed, if you don't want to bother. Regular maintenance includes pruning of plants, weekly watering, and treatment of any pests or diseases. With only one terrarium, this may amount to no more than 15 minutes a week, much less of an investment than fish!
If you go away on vacation for a few weeks, fill up the saucers, cover the terrarium up a bit more with the glass to keep evaporation low, and don't worry. Most cp's can easily survive for that length of time without you!
Suitable plants
Many plants are suitable. These include sundews, pings, bladderworts, Byblis, Cephalotus, and Nepenthes. It's best to avoid temperate varieties that require a cool dormancy period, unless you're able to provide this for them.
Good luck with your terrarium!