Closed terrarium - The 10 most frequently asked questions

If you have heard about closed terrariums for the first time and now want to build one yourself, you are probably asking yourself a few questions. To help you find all the answers for a closed terrarium quickly, I've briefly answered the 10 most common questions here. Note that closed terrariums are much more detailed than you might think at first, so not all answers go into deep detail. However, I have linked you to more resources below the answers where you can read on directly.

#1 How long does a closed terrarium last?

If you take proper care of your closed terrarium and meet all the conditions in it optimally, it really will last forever. If the water, oxygen, and nutrient cycles in an closed terrarium are all met, there will always be enough resources to sustain life in it.

The oldest closed terrarium in the world belongs to David Latimer of England. He built it back in 1960, making it 61 years old today. In all that time he never opened his closed terrarium and it still sprouts. If nothing happens to the closed terrarium and it continues to stand where it did, it will last forever.

#2 How does a closed terrarium work?

A perpetual terrarium works because of the three cycles I just mentioned. These are the water cycle, the oxygen cycle and the nutrient cycle. These ensure that the initial conditions in a closed terrarium are constantly reforming. This allows new life to form constantly.

It is important that the container for the closed terrarium is also really airtight. Otherwise, water will escape in the long run and interrupt the water cycle. Without a steady supply of new water, the other two cycles will break down as well. If you haven't already clicked the link above, you can read in detail how a closed terrarium works here. Translated with www.DeepL.com/Translator (free version)

Oxygen cycle in a closed terrarium with animals
Oxygen cycle in a closed terrarium

#3 How do you build a closed terrarium?

Building a closed terrarium is really not difficult. In principle, you only need an airtight container, a few stones, some soil, water and plants. From these materials you make a false bottom, a loose substrate and finally a beautiful little world.

Unlike with normal pots or terrariums, however, you have to make sure that you get all the conditions right on the first try. You close the glass and don't want to open it again. Here you can find a step-by-step guide for a closed terrarium.

#4 Do you have to care for a closed terrarium?

No, actually, you do not need to care for a closed terrarium. This makes it perfect for people who don't have a green thumb. As soon as you close the glass, an ecosystem forms in an closed terrarium, which is stable in the best case and will then also remain alive forever.

However, you may want to clean your closed terrarium at some point. In the long run, the plants and animals will leave dirt on the walls. Algae will form, making it difficult for you to see. Fortunately, there are tips and tricks to clean an closed terrarium.

Green algae in a closed terrarium
Green algae and other dirt

#5 Which plants are suitable for closed terrariums?

In principle, all plants whose natural environment you can recreate are suitable for closed terrariums. There are easier plants, like moss, or more difficult plants, like orchids or carnivorous plants. Especially orchids are difficult to keep, but it is not impossible.

Here are examples of appropriate plants for closed terrariums.

Additionally, you'll find ideas on how to present orchids in closed terrariums.

#6 Which animals are suitable for closed terrariums?

Here, too, a variety of candidates come into consideration. Since closed terrariums are usually much smaller than normal terrariums, larger animals such as lizards or frogs are definitely out of the question. You cannot intervene directly there and also do not notice in time if there is too little oxygen.

However, small insects, such as beetles, but also spiders, snails and worms are eligible. Two critters that are perfect for closed terrariums (but are not actually insects) are springtails and woodlice. Both feed on plant debris, making them the perfect clean-up crew for your closed terrarium.

Here you will find 5 types of animals for a closed terrarium. In addition, here is also a article about springtails and a article about woodlice.

Closed terrarium springtails
Springtails. Source: AJC1 at Wikimedia Commons, CC-BY SA 2.0

#7 What is the difference between closed terrariums and bottle gardens?

The two terms closed terrarium and bottle garden are often used and are usually synonymous. They both refer to sealed containers with plants inside. In Germany, the term bottle garden is much more common. The closed terrarium only gained prominence in 2016 through the YouTuber SlivkiShow.

Personally, I'm really only talking about bottle gardens when it's actually a bottle as a container. But that's just personal preference.

You can also learn more about the origins of the terms closed terrarium and bottle garden, the Wardian case, and other terms like hermetosphere and biotope here.

#8 What is the difference to a normal terrarium?

The difference to a normal terrarium is that a closed terrarium is closed and in the best case you don't have to take care of it after the initial setup. However, this also leads to the fact that most closed terrariums are plant terrariums and do not feature larger animals.

However, they are super suitable for people with little time or those who live alone at home because of the low maintenance.

#9 Should you buy a closed terrarium?

Whether you build a closed terrarium yourself or buy it ready-made is a total matter of taste. Nevertheless, both variants have their advantages and disadvantages. On the one hand, self-made closed terrariums allow you much more flexibility in terms of creativity, of course, but on the other hand, you have to think about everything yourself.

Ready-made, closed terrariums are usually available as a complete set or you only have to plant the plants into them. This takes away a lot of thought, but also creativity. Nonetheless, they make great gifts for a friend or relative. Here you can find a whole discussion if you should buy closed terrariums ready-made.

Also, here's a review for the Ecoworld Jungle Biosphere if you want to look at a finished terrarium right away.

#10 How much water does a closed terrarium need?

The amount of water is absolutely crucial for a closed terrarium and will ensure in the long run whether it survives or not. The exact amount depends on the size of your tank and the amount of plants you have. While there is no way to determine this across the board, luckily there are a few tricks for this as well.

An ideally watered closed terrarium will be fogged up in the morning and relatively dry in the afternoon. How you create the correct amount of water for a closed terrarium with this clue, you can also read here.

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