Tarantula Substrate Guide: Which Is Best And What Should You Know About It?

I love nothing more than to buy a new terrarium (preferably Exo Terra) and spend time to build up a habitat for tarantulas. Mixing bags of wood, moss, bark, but foremost the substrate, to turn it into the resemblance of the natural habitat for my tarantula.

However, there are many substrate products to choose from. As a beginner, it can be overwhelming which one you should choose. So let’s discuss which substrate is best and what you should know more about the substrate.

A proper substrate is essential to the health and happiness of your tarantula. I personally recommend using coconut fibre (coir), with or without substrate additives, depending on your tarantula species. Coconut fibre is a clean product with good consistent quality, and tarantulas seem to love this substrate. Besides that, coconut fibre has a positive effect on the enclosure’s humidity and won’t mould quickly.

But there is more to know about the substrate. And besides coconut fibre, other substrate products or a combination of these products work well too. It is also important to know which substrate products you should avoid at all times. These products are not liked by your spider and, in some cases, even harmful or deadly to your tarantula.

What is the best tarantula substrate?

There are many different preferences about the substrate among tarantula keepers. Much is up to personal choice. We discuss the more popular choices of products that are used.

Coconut fibre: My #1 pick

My number one pick for a tarantula substrate is without a doubt coconut fibre — also called coir or coco fibre. Although this product was originally designed to be used for gardening, because of its texture, visual appearance and lack of any minerals and additives, it is a popular choice to use.

Coconut fibre can be bought at garden centres in large bags, or as compacted coconut fibre bricks. Although the bags are somewhat cheaper, because it is only sold in large bags, many prefer the compacted bricks.

You only need to add water to it, so it will expand. Then drain the excess water and it is ready to use for your enclosure.

Topsoil, potting compost and potting soil

These three products (still there are small differences) can work well for your tarantula enclosure. The texture and visual appearance look exactly like a forest floor, which is the natural habitat of most species. It is a popular choice among many keepers and also much cheaper than coconut fibre.

When choosing for soil/compost, you need to look out that you buy a product without any additives and fertilizer. Even when it is stated to be organic, it can still contain additives that are unhealthy for your spider.

It would best to buy these products and not collect it from outside in nature. If you do so, you will also transfer unwanted (micro)organisms with it, that can irritate or harm your tarantula eventually.

When you collect soil from nature, boil it in water to kill unwanted parasites, bacteria and other pests that may be present in the soil. Also, collect soil from an area that is not close to potentially fertilized land.

Peat moss

Moss can also be used as a tarantula substrate. Peat moss is often available in compacted bags. When water is added, it will expand, and it is ready to use. Like soil, choose moss that is free of additives and fertilizers.

Because moss is a plant, it can absorb water really well, and release it slowly what benefits the humidity. This is especially useful for tarantula species that require higher levels of humidity.

The main downside is that burrowing species can’t burrow in it. For that reason, it is not suitable for some species. Also, some terrestrial species don’t like walking on moss, but that differs per individual.

Additives: Vermiculite/perlite and spagnum moss

For a long time, vermiculite was the most recommended substrate and considered as the “ultimate” product to use for a tarantula substrate.

Nowadays, it is not considered to use as a standalone product anymore, but can still be very useful when mixed with another base substrate like topsoil or coconut fibre. This becomes especially true when you want a substrate that maintains high humidity levels.

Vermiculite (and also perlite) is an inert mineral compound which can absorb a vast amount of water. It is also a very clean product, where fungus seldom grows on it. However, it lost its popularity because tarantulas simply don’t like to stand on it.

Sphagnum moss is used in the same way for the same reason. It can absorb moisture really well and create a higher humidity. However, also sphagnum moss is not considered as a product well to use only on its own. Tarantulas can’t burrow in it and many don’t like to stand on it. Although, you can consider sphagnum moss when keeping an arboreal tarantula species.

Substrates that you should avoid!

Although there are many choices to pick from, from experience, there are also some products that should be avoided at all times. Tarantulas do not like these products. Some products are even harmful or can be deadly to your beloving spider. So I recommend that you don’t use any of the products listed below!

Pine chips and other cedar products

Products made from cedar and conifers are considered to be harmful to tarantulas. These trees have resinous sap that is very unhealthy for tarantulas. So don’t use these products or products that contain this as an ingredient.

Bark chips

For tarantula keeping, they are far from ideal to use as a substrate. Even the finer dark chips, that are sold as reptile substrate, should be avoided. And there are a number of reasons for that.

First and foremost, they don’t absorb moisture well and when sprayed stay quite wet. Perfect conditions for mould to grow. But they also tend to rot rather quickly in humid and warm(er) environments.

Terrestrial tarantulas don’t like bark chips as substrate, and fossorial species can’t proper burrow in it. So it has no perks to use it.

Corn cob granules

Corn cob granules are readily used for reptiles that require a desert-type environment. However, these granules tend to get mouldy quite rapidly with higher humidity. Although it comes to personal taste, it also doesn’t look great in the enclosure.

When used in a tarantula enclosure, you continuously need to refresh your substrate, which is not ideal and may be stressful for your spider. Tarantulas don’t like change in their environment.

Sand

Although sand does not make the worst substrate there is, it is still unfavoured to use. The first of foremost reason is the lack of water absorption and retention. Sand becomes muddy rather quick, creating pools of dirty water. You can imagine that for burrowing species, there burrow quickly fill up with water.

Sand is also quite heavy and will compact easily to a hard and useless layer of a substrate. Because of this compaction, there is not much air flowing through the substrate, causing the sand to become dirty and smell.

Gravel & aquarium gravel

Gravel, also the one for aquariums, are rather useless for tarantulas. It does not absorb any water and makes it difficult to maintain the correct humidity.

Tarantulas don’t like to stand and walk on gravel. Earlier reports note that tarantulas continuously try to climb up (even terrestrial and fossorial species) to avoid standing on the gravel.

Gravel can be quite sharp too, which make a risk that the tarantula harm itself. When falling, a rupture or cut can happen quickly with gravel.

Although it does not get mouldy, it has not any perks to use as a tarantula substrate.

Fertilizers and chemical additives

We mentioned it before, but always avoid products with added fertilizer or other (chemical) additives. Even when it is stated as organic, it can still contain additives that are unhealthy for your tarantulas.

Fertilizer and additives can poison your tarantula, or irritate their exoskeleton. When evaporating in an enclosed space like a terrarium, it can also affect their lungs and respiratory system.

Reason enough to avoid it at all times.

Sharp materials

Anything sharp or sticky should be avoided to use in the substrate. Tarantulas are despite their exoskeleton and fearsome looks quite delicate animals.

When scratching and cutting at, or falling on, any sharp material can irreversibly harm and damage your beloving tarantula. So make sure your substrate is safe for your friend.

The importance of the substrate

We described a little about why the substrate is so important in your tarantula enclosure. But there is more to it than meets the eye. So let’s have a quick look at the important role of the substrate in your tarantula enclosure.

• Soft carpet: The substrate serves as a soft carpet for your spider. Tarantulas (except arboreal species) prefer a softer forest-floor type substrate. A soft carpet also prevents damage when falling. It is a little bit the same as your carpet at home, right?
• Isolation and temperature buffer: And as your carpet at home, it also serves as isolation. When having a thick layer of substrate in your enclosure will reduce heat loss. It is like a temperature buffer, where heat is stored and when cooler be released slowly.
• Maintain humidity: We mentioned already a couple of times. The substrate is the buffer to maintain your humidity. Depending on which substrate your choose determines this humidity buffer. When using coir with vermiculite, for example, has a huge moisture absorption capacity, but also release it slowly for a long time, creating a higher humid environment. A humid environment keeps your tarantula hydrated, healthy and happy.
• Burrowing: For fossorial species, the substrate is a must-have for the way they live: creating and hiding in their burrows. Without substrate, they absolutely won’t be happy. Remember, not all substrate types are suitable for burrowing tarantula species.
• Cleanliness: It sounds a bit controversial, but a substrate contributes to the cleanliness of the enclosure. But, without a substrate, it is easier to clean, right? Well, let me explain. The substrate holds the dirt in the enclosure, and with refreshing a part of the substrate also removes these dirt spots (we also call this spot-cleaning). Another way is that your substrate can hold a clean-up crew. These little creatures help you keeping the enclosure clean and free of mould.
• Aesthetics: And last, we like to take a little bit of nature into our homes. We can recreate small ecosystems. Substrates make the enclosure look more aesthetic and provide a more natural feeling.

Match the substrate with your tarantula

Different types of tarantulas have different needs and requirements for the substrate you use. Therefore it is important that your substrate match with your tarantula. We differentiate three types of tarantulas.

The list below is a general guidance to choose the best substrate for your species. However, always research your species to decide which substrate is best for your tarantula. Choosing 100% coconut fibre is a safe choice to start

Terrestrial tarantulas (ground-dwelling species)

Most people, and I can recommend you to do so too, start with a ground-dwelling tarantula species. Generally, terrestrial species will do very well on a substrate purely of coconut fibre. They don’t have humidity requirements and are perfectly fine with this soft bedding.

Coconut fibre is easy and clean, and the coconut fibre (bricks) are always the same in quality. You don’t need to worry about added fertilizer or chemicals, or mixing ratio with other products (although you can experiment with that after some experience, of course).

Topsoil is my second preference to use for this type of tarantula species.

Fossorial tarantulas (burrowing species)

For tarantulas that like to burrow, coconut fibre can work really well. Although you need to make sure you compact it enough so that your tarantula can make the actual burrow.

For this species, I like to mix the coconut fibre with topsoil or potting earth, to make the substrate more compact and easier for them to burrow.

Don’t worry, tarantulas are resourceful, and quickly will make a burrow and fortify them with webbing. They web the sides of their burrow, so it prevents from collapsing.

Arboreal tarantulas (tree-dwelling species)

With arboreal species, the tree-dwelling tarantulas, you generally need higher humidity in the enclosure. With these species, I like to choose a mix of coconut fibre or topsoil, mixed with vermiculite and add some moss to it.

You can also consider using peat moss when you wish to maintain higher humidity. Peat moss works really well with arboreal type tarantulas.

Additional recommendations for your tarantula substrate

• Substrate volume: How much substrate do you need, you might ask? A substrate should be between 7cm (3″) and 10cm (4″) for terrestrial species. Arboreal species can do with less. However, burrowing species need a thicker layer to burrow. They should have a substrate layer around 20cm (8″) to comfortably digging in.
• Substrate durability: Quality substrate can endure for a long time when properly maintained. You can keep a substrate for several months, even years, before it needs a refreshment. And that is a good thing because tarantulas don’t like changes in their environment.
• Maintenance of the substrate: Important is that you keep your substrate in good condition. First your need to keep it damp, so once a while you need to spray it. Secondly, your tarantula will make a mess, although they are quite neat. Do some spot cleaning to take out the dirt, faeces and uneaten prey items. This will prevent the growth of mould so that your substrate can last a long time.
• Decoration: Making your enclosure look great can be an enjoying task. Add objects like cork, wood and live plants to your enclosure to make it look more natural. Adding live plants will turn your enclosure in a real habitat. But keep in mind that you don’t place heavy objects in the enclosure, especially with burrowing tarantulas. Beside that heavy objects like stones will compact your substrate too much, it also increases the risk that burrows made by your spider may collapse. Choose lightweight materials.

What does a substrate cost?

How much does a substrate cost? This will depend on the species you have, the substrate your choose, the enclosure size you house your spider, and which country you live.

To give you some direction of the costs we listed below the prices of commonly used products. You can collect substrate from nature which will be free, of course. However, when you do so, make sure you boil the substrate before placing it in the enclosure. It is much easier and less messy to just buy the substrate. It is not that much of a cost.

Product	Price per liter	Price substrate layer (8L)	Price/bag
Coconut fibre	$0.50 /	$4.00 / €3.38	$4.00 / €3.38 (~8L)
Topsoil	$0.11 /	$0.88 / €0.74	$2.25 / €1.90 (21L)
Potting soil	$0.11 /	$0.88 / €0.74	$2.25 / €1.90 (21L)
Peat moss	$0.12 /	$0.96 / €0.81	$9.99 / €8.45 (85L)

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