Perlite: Ideal for a Terrarium Substrate

Perlite is light, porous, stores water and is also pH neutral. This makes it an ideal admixture for a terrarium substrate. But what is perlite anyway?

Perlite is a volcanic rock that offers many benefits for your terrarium. In this article you will learn why you should always consider it for your terrarium substrate in the future.

What is perlite?

Perlite is a volcanic rock composed of obsidian. Obsidian is a black glass that is formed when lava cools rapidly. When obsidian contains water and is exposed to high temperatures, it expands and breaks into small white beads or shards.

If you're looking for a really in-depth explanation of how it's made, check out Dicalite.

As it expands and fractures, it has a very porous structure that can hold air and water. In addition, perlite is pH neutral and mineral, which means that it does not contain or emit nutrients.

Perlite on dark wood
A pile of coarse perlite. Source: Lusnem, Wikimedia Commons, CC BY-SA 4.0

Why is perlite a good substrate for terrariums?

Perlite has many properties that make it an ideal substrate admixture for terrariums. Due to its water-retaining property, it prevents waterlogging, which can drown the roots of your plants.

Just like a sponge, it holds water on its surface. It then releases this moisture back to the plants over a long period of time. This is especially important for tropical terrariums, which require high humidity.

Unlike salt, which can also store water well, perlite is absolutely harmless to your plants. In principle, they do not even notice that it is there.

However, Vermiculite is still superior in the water-retaining property. We will come to that further down.

Another great feature of perlite is that it keeps your substrate loose, improving aeration. The flowing water can't compress your substrate as much, allowing your plants' roots to take up more oxygen.

You can learn more about terrarium substrates in the following article.

Why mix perlite into your substrate?

Perlite alone is not a complete substrate for terrariums. It contains no nutrients and provides no support for the roots of the plants. Therefore, it should always be mixed with other substrates or materials.

For example, you can combine perlite with soil (coco hum, peat-free soil), pine bark (4-8mm), moss or other organic matter. This improves the structure, aeration and nutrient supply of the substrate.

The mixing ratio depends on the type of plants or animals you want to keep in your terrarium. A rule of thumb is: The substrate should dry out within one, but at the latest two weeks! If you're building a perpetual terrarium, of course, that doesn't quite apply. Here you have a daily water cycle.

How to choose the right one for your terrarium?

Not all perlite is the same. There are different grains and qualities, suitable for different purposes.

For terrariums you should choose a fine to medium grain size of 0 to 6mm. Although 0mm as a grain size sounds a bit strange at first, but that is how it is specified. This only means that the grains can be virtually unlimited small.

A grain size of 0 to 6mm ensures good water retention and air circulation in the substrate, allowing the plant roots to absorb more oxygen.

Some perlite scattered on the ground in a greenhouse. The perlite is coarse and has white, light gray and gray colors. The soil is dark brown and moist. The greenhouse is full of green plants and flowers that contrast with the perlite.
A pile of perlite on brown earth

How to prepare it for your terrarium?

Before adding perlite to your terrarium, you should wash it thoroughly and let it drain. This is important to avoid mold or fungal infestation.

You can wash it under running water or soak it in a bucket of water and then drain it through a sieve. After washing, you should drain the perlite well or spread it out on a towel to remove excess water.

What is the difference between perlite and vermiculite?

Perlite and vermiculite are two similar materials often used in horticulture and greenhouses. Both are volcanic rocks that expand when exposed to high heat and become lightweight and porous materials. Both can store water and improve soil drainage and aeration.

By the way, here's the article on vermiculite: Vermiculite: Why It Belongs In Your Terrarium Substrate.

However, there are some essential differences between the two.

The main difference is that vermiculite mixes with the soil and helps bind water. Perlite, on the other hand, increases the drainage of the soil and does not mix with the soil.

This means that vermiculite is better suited for plants or animals that need constant moisture, while perlite is better suited for plants or animals that need good drainage.

Vermiculite is much darker compared to perlite
Vermiculite is much darker in color. Source: I, KENPEI, Wikimedia Commons, CC BY-SA 3.0

Another difference is that vermiculite has a dark brown to golden brown color and is shaped like flakes when dry. Perlite has a white color and looks like small granules or foam balls.

Color is always a matter of taste, of course, but you should keep that in mind and consider which one suits you better when mixing your substrate.

Where to buy perlite?

Affiliate note: I receive a small commission for some of the products linked in this article, if you buy them through my links. This won't cost you any more than usual! I recommend all of these products based on my honest opinion and not because of the commission I receive. As an Amazon Affiliate I earn through qualified sales. For more information, please read this affiliate note.

Perlite is a common material that you can find in many garden centers or online stores. One of these online stores is of course Amazon. There is a large selection there. Here you can find some.


Now you know what perlite is and what you can use it for. It is the ideal admixture for a terrarium substrate because it is light, porous, water retentive and pH neutral.

I hope this article has helped you to learn more about perlite. If you have any questions or suggestions, feel free to comment below the article.

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