If you’ve been in the hobby a long time, you’ve probably seen many different substrate options come and go in popularity over the years. What was deemed the best tarantula substrate a couple of decades ago is completely different to the majority of today’s opinions. It wasn’t uncommon to see tarantulas being kept on 100% vermiculite a couple of decades ago, as well as to not provide a deep substrate. Nowadays, if you did that and posted it on a forum, you’d be bombarded with abuse.
I’ve done my fair amount of experimentation too, which is half the fun. There is definitely not a one-option-fits-all situation when it comes to substrate. Regional differences, as well as tarantula requirements, will completely change what is required and what is tolerated by your spider.
If you speak to a few seasoned tarantula keepers, you will likely get slightly different results from each of them. This is because a lot of people will mix and match multiple substrates to create the consistency that they want. For a novice keeper, though, this is unnecessary for the most part.
Below we have listed the best and most common substrate options available, as well as products that you should avoid.
Coco fibre (coir)
Coir, which is more commonly known as coco fibre, is a product that was originally designed to be used for gardening. It creates a similar effect to soil, in regards to its texture and visual appearance, but just doesn’t have any of the minerals and other additives that soil has. It’s an eco-friendly product and is created from renewable sources.
Coco fibre can often be bought from your local garden centre, but the consistency will vary. It’s usually in large backs and not compacted tightly, which means you will need to store a large bag of coir if you don’t need to use it straight away.
Due to the size of garden centre coir options, a few companies have developed coco fibre bricks that are made from very compacted coco fibre. All you need to do is add water, watch it expand to several times its original size, and then drain the water. After that has been done, it’s ready to be used in your tarantula terrariums.
Coco fibre is often mixed with other substrate options by keepers, to create a consistency that better suits the specific tarantula. Adding small amounts of sand, top soil, and even vermiculite can create different substrate effects and compositions.
For the reasons above is why coco fibre is the best substrate for tarantulas without a doubt.
Regular topsoil that you can purchase from your local garden centre can be a fantastic choice for tarantula terrariums, either by itself, or mixed with coco fibre.
If you do plan on using topsoil, it’s essential that you check that it is a product without any additives, like fertiliser, regardless of where it is organic or not.
Topsoil works well for species that don’t need anything ‘special’. A lot of people have reported that they have used topsoil from their gardens without any issues. My only advise with this is, if you do plan on using substrate or decor from outside, is you bake everything in the oven or boil it in water (depending on what it is). By doing so will kill any parasites and unwanted bacteria that may be present.
Just like topsoil, care should be given when purchasing peat moss as you will want to choose a product that is completely organic and contains no fertilisers.
Vermiculite is a mineral substrate that can absorb an incredible amount of water. Back in the day, it was very common for people to keep tarantulas on 100% vermiculite. It was deemed as the ultimate substrate.
Luckily, those days are long behind us now. Especially as it’s usually quite easy to see how much tarantulas don’t even like standing on it (look for them standing on their ‘tip toes’.
However, vermiculite still has its place in the tarantula hobby. It’s more commonly used as an additive to other substrate materials, to aid in water retention and humidity.
Substrates to avoid
Now that we have listed what we believe to be the best substrate options available for tarantulas at the moment, we thought it would be beneficial to list the substrates that you should absolutely avoid.
Although we can’t realistically list every single one, we shall briefly cover some of the more common bad choices that new and old keepers have used in the past.
You may have noticed that we listed sand above, but that should only be used in small quantities when being added to another substrate medium. While sand isn’t the worst, it isn’t great. It will not hold water well, burrows will collapse, and a lot of tarantulas will probably not even like to stand on it.
Feel free to sprinkle some on the top of your substrate though, or mix a small amount in.
There are a lot of different bark chip options available on the market that are most commonly sold in reptile shops. For their created purpose, they work great. However, for tarantula keeping, they are far from ideal.
Bark chips don’t hold moisture well, and they are very prone to becoming mouldy and rotten in continuously humid environments. The also make it next to impossible for a tarantula to construct a burrow.
Unfortunately a lot of reptile shops, who perhaps don’t know any better (even though they should), will advise that this substrate is good when selling a tarantula.
Just like most animals, tarantulas really dislike standing on gravel. They dislike it so much that they will try their hardest to climb their enclosure, just so they don’t have to stand on it. As you can imagine, this may increase the chances of the tarantula falling and hurting itself, as well as the added stress factor.
While gravel doesn’t go mouldy, it also holds almost zero moisture.
However, by all means add a few pieces to your enclosure to make it look more aesthetically pleasing, if you wish.
Corn cob granules
Another reptile-focused substrate, corn cob granules are another substrate that should be avoided at all costs. This substrate can go mouldy very quickly and will need to be replaced often. It also looks pretty unsightly.
What is the best tarantula substrate overall?
The simple answer to this, is coco fibre (coir). It’s a fantastic product, can be used for every single type of enclosure and environment, and becomes in compressed brick form.
A more advanced answer, would be coco fibre and a mixture of other substrates like topsoil and sand. This allows you to create a more natural substrate that may benefit your specific tarantula more than just using only coco fibre. It also means that you make your coco fibre last a lot longer.
Best substrate for burrowing tarantulas
As we have mentioned briefly above, the best substrate options to allow a tarantula to burrow well would be coco fibre, topsoil, or a peat moss mixture. The most important thing is to ensure that you pack your substrate down hard. This allows your tarantula to construct a burrow a lot easier than if it was loose. However, don’t worry too much about its tunnel collapsing, as they will web it up so much that it really should never collapse.