Tarantula Substrates: What’s Best?

Tarantula keeping has come a long way since its early days.

We now have more species available, new types of cages and a better understanding of tarantula husbandry than ever before. In terms of keeping tarantulas, one of the most hotly-contested subjects is that of tarantula substrates.

Each have their own strengths and weaknesses but what really is best?

Best Tarantula Substrates

Let’s start with the good substrates; the ones I strongly suggest that you focus your time on. Use one or more of these (in combination) and you shouldn’t go too far wrong…

Coco Fibre (Coir)

Coir makes an ideal tarantula substrate.Coco fibre, also known as coir, is an eco-friendly product which has long been popular with gardeners.

This product looks and behaves quite like compost, but comes from renewable resources (unlike peat moss).

It can be bought in bags from garden centres but most tarantula keepers choose to buy highly-condensed blocks of coir made specially for reptile keepers.

These are simply soaked in water for a few minutes, whereupon they will absorb water and expand. Simply drain away any excess water and use in your tarantula cage.


  • Looks great
  • Easily stored in brick form
  • Excellent for digging species
  • Good water absorbency


  • Not the cheapest substrate available
  • Takes up to 30 minutes to fully expand so not ideal for a quick clean-out

Vermiculite & Perlite

Scorpion on vermiculite substrate.These two products are inert mineral compounds, capable of absorbing huge amounts of water.

When I first started keeping tarantulas back in the early nineties (I kid you not) vermiculite was considered the “ultimate” tarantula substrate.

These days things have moved on rather, with many keepers believing that their pets dislike standing on it.

While vermiculite still certainly has its place, it is now more commonly used as a mixer – such as with potting compost.

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Using it in this way the substrate isn’t unpleasant to stand on and yet helps to retain moisture in the cage.


  • Absorbs plenty of water
  • Rarely if ever attracts mould
  • Very light
  • Freely available from garden centers


  • Looks pretty unsightly
  • Some tarantulas don’t seem to like it

Potting Compost

Potting compost is another popular substrate which is available cheaply from most garden centers. It looks attractive and provides excellent opportunities to burrow for those species so inclined.

The only real downside I have found while using it is that some composts dry out quite quickly – hence why some people choose to mix in some vermiculite.


  • Cheap to buy
  • Easy to source
  • Looks good
  • Ideal for burrowing


  • Can be heavy
  • May attract mould
  • Avoid composts with added chemicals (fertilizers etc.)
  • Avoid composts with large chunks in them


Moss as a substrate in a reptile cage.Moss can be bought in compacted blocks from many reptile stores, soaked in water and then used as a tarantula substrate.

The good thing about moss is that it can look really smart in a tarantula cage and is excellent at absorbing water.

On the downside, of course, moss doesn’t allow your tarantula to burrow which for some species can be a handicap.


  • Looks awesome – rainforest setup anyone?
  • Absorbs loads of moisture
  • Lightweight


  • Useless for burrowing species

Want some inspiration? Check out this collection of exotic pet set-ups I’ve been gathering to see just what’s possible with a little time and effort…

Follow Keeping Exotic Pets’s board Reptile Enclosures & Terraniums on Pinterest.

Bad Tarantula Substrates

So that’s the winners out of the way.

However while it would be impossible to ever list every bad choice of substrate, it does make sense to list some of the more common suggestions seen so that you can understand why they should be avoided…

Bark Chips

Bark chips come in a range of forms. There are fine dark chipping often sold as “rainforest bark” in reptile shops and there are lighter chippings such as beech which is popular among snake keepers.

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All of these options though have a number of weaknesses.

Not only do they absorb very little moisture but they’re also highly likely to go mouldy and start rotting in the warm and humid environment that tarantulas need.

Added to that the fact that they aren’t ideal for burrowing, these substrates generally have very little application for tarantula keepers.

Corn Cob Granules

Corn cob granules may be environmentally sound, and popular with reptile owners with desert-type reptiles, but once again these granules tend to rapidly go mouldy and need to be constantly removed and replaced. Not an ideal substrate.


Sand isn’t necessarily the worst substrate out there, but tends to be very heavy and doesn’t make for very good water retention.


Tarantulas seem to dislike standing on gravel and will spend much of their time trying to climb up the walls of their cage away from it. This can lead to damage if the spider falls so should be avoided.

While it doesn’t tend to go mouldy, for obvious reasons it is next to hopeless for retaining moisture in the cage.

Conclusion: What Is the Best Tarantula Substrate?

Personally after keeping literally thousands of tarantulas over the years I believe that the very best substrate for tarantulas is coir.

It is light, friable, excellent at retaining moisture and just looks great. As a second choice I would opt for potting compost combined with some vermiculite to retain moisture (3:1 ratio or there abouts).

On top of this I often (but not always) use small amounts of moss just to decorate the cage. As I’m  very into naturalistic setups for my exotic pets,

I love nothing more than to buy a new Exo Terra and spend some hours with bags of moss, bark, wood and so on to turn it into the semblance of a tropical rainforest.

Tarantula substrate pictures c/o The_Gut Furryscaly & @TripDawg


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