Vermiculite: Why It Belongs In Your Terrarium Substrate

Vermiculite is a clay mineral that belongs to the phyllosilicates and is formed by weathering of rock. It is used for various purposes, but is especially interesting as a substrate for terrariums. In this article you will learn everything you need to know about vermiculite.

What is vermiculite?

Vermiculite is a mineral from the mica group and consists of aluminum, iron or magnesium silicate.

It forms leafy, flaky or massive crystals, but unfortunately their appearance is not one of their main selling points. It can vary from colorless to gray-white to yellow-brown or green. However, it has another important ability instead.

It is one of the clay minerals that contribute significantly to soil fertility due to its ion exchange ability, making it ideal for a terrarium.

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

Why is vermiculite a good substrate for terrariums?

Vermiculite has many benefits as a substrate for terrariums, both for the plants and the animals that live in them. Here are some of them:

Vermiculite improves soil fertility by storing nutrients and slowly releasing them to plants. For example, it can absorb fertilizer and prolong its effect. It also retains moisture and increases the air capacity of the soil. It thus prevents waterlogging and dehydration, which are harmful to many plants and animals.

By the way, here you can find all the info about substrates in general: Substrate For A Closed Terrarium - All You Need To Know.

It also provides a habitat for the animals in the terrarium, especially those that like to burrow or hide. It is soft, loose and insulating and protects the animals from cold or heat.

It suppresses weed growth as a cover material (if you use it as the top layer), preventing pest or disease infestation.

And last but not least, it is environmentally friendly and sustainable because it is a natural mineral that can be recycled or composted.

Why should you use vermiculite?

You may be wondering why you should use vermiculite when there are other substrates for terrariums.

The answer is simple: Vermiculite is one of the best substrates for terrariums because it can adapt to different types of terrariums. Whether you have a terrarium with succulents, orchids, cacti, bromeliads, carnivorous plants or other exotic plants, vermiculite can help you keep them healthy and beautiful.

But vermiculite is not only suitable for plants. It is also a great substrate for animals. It can be used as a breeding substrate for reptile eggs, because it optimally regulates the humidity and temperature.

How do you choose the right vermiculite for your terrarium?

Now you know why vermiculite is a good substrate for terrariums. But how do you choose the right one for your terrarium? There are some criteria you should consider before you decide. Here they are:

Vermiculite is available in different grain sizes, from very fine to very coarse. The grain size influences the properties, such as the water storage, the ventilation and the structure. Depending on what plants or animals you have in your terrarium, you should choose an appropriate grain size.

A small bowl filled with vermiculite. The bowl is made of ceramic and has a floral pattern. The terrace is surrounded by plants and flowers in pots and baskets.
A small bowl with vermiculite

Fine grain

The fine grain size of 0-3 mm is ideal for small and soft-shelled eggs, such as those of geckos, chameleons or frogs. It retains moisture well and prevents the eggs from drying out. It is also good for plants that require high humidity, such as orchids or bromeliads.

Medium grain

The medium grain size of 1-4 mm is a good compromise between moisture and aeration. It is suitable for most plants and animals in the terrarium, as it provides a good balance between water and air supply.

Coarse grain

The coarse grain size of 3-6 mm is ideal for large and hard-shelled eggs, such as those of pythons, iguanas, monitor lizards or other lizards. It causes better aeration of the eggs and improves gas exchange, which is important for breeding success.

It is also good for plants that need good drainage, such as succulents or cacti.

Many reptile breeders therefore mix coarse and fine vermiculite in a 1:1 ratio to obtain the optimum grain size for their eggs.

How do you prepare vermiculite for your terrarium?

After you have chosen the right one for your terrarium, you need to prepare it briefly before using it in your terrarium.


Although vermiculite is a clean substrate in itself, it may of course contain dust or dirt that you should remove before use. You can rinse it in a colander under running water until the water runs clear. Then let it drain well and dry.


Depending on what plants or animals you have in your terrarium, you can mix vermiculite with other substrates to improve the properties of the soil. For example, you can mix it with soil, sand, peat or coconut fiber.

The ratio depends on your preferences and needs. You can also create different layers of different substrates to create different zones in your terrarium.

What is the difference between vermiculite and perlite?

Vermiculite and perlite are two related materials commonly used in horticulture and greenhouses. Both are volcanic rocks that expand when exposed to high heat, becoming lightweight and porous materials. Both can store water and improve soil structure.

By the way, you can find the article about perlite here.

However, there are some important differences between the two in various aspects.

  • Water retention: Vermiculite binds water in the soil and slowly releases it to the plants. Perlite improves the drainage of the soil and prevents waterlogging.
  • Nutrient supply: Vermiculite has a high ion exchange capacity and can store and release nutrients. Perlite has a low ion exchange capacity and does not affect the pH of the soil.
  • Structure and color: Vermiculite has a foliated or flaky structure and a dark brown to golden brown color. Perlite has a spherical or irregular structure and a white or gray color.
  • Suitability for incubators: Vermiculite is soft and light and protects the eggs in the incubator from pressure or movement. Perlite is hard and sharp-edged and can damage or injure the eggs in the incubator.
Perlite on dark wood
Perlite is significantly brighter. Source: Lusnem, Wikimedia Commons, CC BY-SA 4.0

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

Where to buy vermiculite?

You can find vermiculite in almost all garden centers and in many online stores, such as Amazon. Here you will find, for example, a variant with 8 QT content* and a variant with 103 QT content*, if you need some more.


Vermiculite is a great substrate for terrariums that offers many benefits for the plants and animals that live in it. It is moisture regulating, nutrient rich, insulating and life friendly. It is also ideal as a breeding substrate for reptile eggs, as it optimally regulates humidity and temperature.

To choose the right vermiculite for your terrarium, you should pay attention to the grain size, purity, origin and price. You should also clean it before use, moisten it and mix it with other substrates if necessary.

Vermiculite is not to be confused with perlite, another commonly used substrate for terrariums. Both have different properties and benefits for terrariums. Depending on what plants or animals you have in your terrarium, you can choose one of them or combine them to get the best result.

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