Choosing the Right Substrate for Your Tarantula

Pick your poison…

Since getting into the hobby, I’ve spent a lot of time (more than I’d like to admit) experimenting with various substrates. When I bought my first T about 18 years ago, the popular choice for spider bedding was dry vermiculite. A lot has changed since then, however, and better (and more appropriate) options are now recommended.

Ask any group of tarantula keepers what material they choose to keep their prized pets on, and you are likely to get a variety of responses. A recent poll on the Arachnoboards forum did reveal that there are a handful of popular choices that tarantula keepers mix and match to get the properties they desire. Much is up to personal choice, and I actually find it quite fun to experiment with different combinations.  What follows is a list of some of the more popular choices as well as some pros and cons of each.

COCO FIBER (Eco Earth)

Coco fiber

Made from ground up coconut husks, and sold loose in bags or in compressed bricks, coco fiber substrate has become one of the most popular substrate choices for those who keep tarantulas. Although the bags save you the effort of having to re-hydrate the compressed bricks, they are much more pricey. Zoo Med’s Eco Earth is probably the most popular brand, but other companies also produce the bricks (and some are less expensive).


  • Fairly inexpensive if you purchase it in bricks. Buying bricks in three packs makes it even more affordable. ($7.99-$9.99 for about 21 liters)
  • Absorbs water well for species that need some moisture.
  • Great when used dry for arid enclosures.
  • Seems to resist mold.


  • Can become expensive when filling larger enclosures.
  • Re-hydrating the bricks can be a bit time consuming and messy.
  • Re-hydrated coco fiber has to be dried out before being used in an arid enclosure (I put mine in a large foil turkey pan, then slowly bake in in an oven at about 250°, watching it at all times)
  • When dry, it can be “fluffy” and more difficult for burrowing species to create homes.
  • Dries out quickly (could be a positive with arid species)



Regular old run-of-the-mill topsoil can be a great and inexpensive substrate choice. It can be purchased at any Walmart, Home Depot, or Lowe’s in large bags for only a couple dollars. If using topsoil, it’s important to make sure that it’s organic with no fertilizers added (this includes animal waste). I have found myself using top soil mixes more and more due to the cost-effectiveness, availability, and water retaining qualities. It should also be noted that many European hobbyist have been using regular topsoil from their yards for years with no ill effects.


  • Very inexpensive (a .75 cubic foot bag runs about $2.25).
  • Easily procured.
  • Mixes well with other substrates to get desired properties.
  • Packs down well; good for burrowing species.


  • Inconsistent quality. Often comes with jagged chunks of branches and wood chips that must be filtered out
  • Very heavy when used to fill larger enclosures.
  • If used straight up, spraying/moistening of the substrate can create puddles or mud. It does not absorb water as well as other substrates.



Peat moss is another readily available and inexpensive substrate alternative. Again, it can be purchased in a variety of places, and the large bags are very convenient for filling up large enclosures. As with the top soil, you want to go with a product that is organic and contains no fertilizers.


  • Very inexpensive and comes in large quantities (a 3 cubic foot bag is only $9.99)
  • Packs and forms very well for burrowing species
  • Absorbent when wet down for species requiring moisture.
  • Mixes well with other substrates.


  • Can be a bit dusty if used dry
  • Like top soil, the quality from bag to bag can vary. Large chunks or sticks must be filtered out.
  • Can be prone to growing mold or fungus.

As stated earlier, these three are the top choices among enthusiasts, and each can be used alone, or they can be mixed and matched to create a substrate to fit any need. For the majority of my enclosures, I’ve been using a 50/50 mix of coco fiber and peat moss. This has become my “all-purpose” substrate for many of my specimens.

VERMICULITE (As an additive)


Although the days of using vermiculite as a substrate for my Ts are long over, that is not to say that it can’t be very useful. For species requiring more moisture, I put a 1/2″ thick layer of vermiculite on the very bottom of the enclosure, then mix some in with the 50/50 coco/peat combination and use that to fill the rest of it. I find that the vermiculite retains water better than coco or peat alone, and allows for better water percolation. This enables any water I pour in to filter down to the bottom, keeping the lower levels humid and moist like the tarantula’s burrow in the wild. For Ts requiring more humidity, this also allows the water to evaporate more slowly, elevating the humidity inside the enclosure as it does.

The trick is to not add too much, as overdoing it keeps the soil “fluffy” and prevents it from being packed down well. Vermiculite is relatively inexpensive (an 8 quart bag costs about $3.99), and I always keep some on hand.



Sphagnum moss is another useful additive when you are trying to maintain humidity in an enclosure. Moss absorbs water like a sponge and holds onto it quite well. When used inside an enclosure, it can be wet down to provide a source of humidity. I like to place some around water bowls to soak up the overflow. Although various mosses are produced by reptile supply companies, clean organic horticultural moss can also be purchased at Walmart, Home Depot, Lowe’s, and gardening supply stores.

Some things to avoid when experimenting with substrates:

Anything with jagged sticks or pieces. These could be harmful to the tarantula, as a falling T could rupture its abdomen on something sharp. If you buy substrate with jagged pieces, they must be removed before use.

Substrates with with fertilizers or additives. Make sure to check the labels before you buy. Even some “organic” soils have natural fertilizers added, including animal waste.

Pine chips or products made from cedar. Compounds in conifers and cedar are suspected to be harmful to Ts (Note: it is widely believed that mulches or peat mixes containing pine or cedar products are safe)

Aquarium Gravel. Although used for years, its use as a substrate is now generally frowned upon. Besides holding water too well (it tends to puddle and stagnate beneath the surface), it can trap a tarantulas leg or prove hazardous in a fall.

25 thoughts on “Choosing the Right Substrate for Your Tarantula

  1. Pingback: Quick and Easy DIY Tarantula Enclosure – Arboreal | Tom's Big Spiders

  2. Is Scotts premium topsoil free of additives? Does anybody use this brand? It’s the only one I can find locally, and I’ve looked everywhere within a 100 mile radius. When I search around online to see if anyone has experience with it I get answers ranging from “don’t waste your money on premium just get regular topsoil” to “just use eco earth”, but no actual answers.

    Liked by 1 person

  3. Hey, Tom. Huge fan by the way :-). Which specific vermiculite product do you recommend? I’m unsure which ones to buy because I am not confident if the ones I’ve been looking at are chemical-free or not. Thanks in advance!


  4. Good afternoon,
    I have a B. Albo about 2.5″ and just molted, seems to be doing fine, a little skittish. The top of the substrate(Coco Fiber bought with kit from Jaime’s) seems to have a “dew” appearance. That’s the best way I can describe it. It isn’t all over, but near the water dish, about half the adult cage. Is this something I should be concerned about?

    Liked by 1 person

    • Hi, Jeffrey! Is it moisture on the surface? Jamie usually ships her coco fiber a bit moist, so it could be condensation. With that species (and with the size it’s at(, I would let it dry out a bit.


  5. It’s weird, I don’t think it is moisture, It has been months that I have owned it. I was wondering if it might be some sort of web that that been laid out. I said dew because that’s the best description, kid of like the grass looks in the morning, but I don’t think it is wet. I was just hoping it wasn’t a fungus or something. I haven’t reached in there to feel it, but thought I would ask as it appeared odd.


  6. Hi,
    I am getting both a 3/4 in C versicolor and 3/4 in A urticans Sling, I have their little containers ready but wondered what the best mix of Sub is to keep them at the right humidity as there is not as much substrate for the aboreals. (assuming there only needs to be about an inch or so) I am thinking coco fiber w/ vermiculite but not sure about the ratio. I do have a little sphagnum moss also. Your videos and this blog Rock ! thanks for your contributions..


    • Hi, Nina!

      I use topsoil with vermiculite for most of mine, but coco fiber would work just as well. I’ve found that coco fiber absorbs water very well, but it allow allows for it to evaporate quickly. The vermiculite would help it to retain moisture better. If you put a little pinch of sphagnum behind the cork bark, that will help hold in some moisture, too. Thanks so much!!!



  7. Pingback: Choosing the Right Substrate for Your Tarantula - Arachno

  8. Hi there,

    Would this coir be okay to use? I am over on, any help to my thread would be amazing 🙂 ( (THIS one looks really good value and in bulk @ 0.95p per brick, but has anyone tried it, or is it good/safe for my tarantulas)

    Also will mixing this into the coir above make any difference? (can I user this fine grade vermiculite for my substrate as a mix with coir?),p_72:419153031




    • Hello! You just want to make sure that the stuff you used doesn’t have any additives. I get 10 lb bricks of coco fiber now, and I pay about $17. The stuff I use has no additives and is meant for planting. It works wonderfully, and makes a LOT of coco fiber when hydrated. Both of those look good to me! 🙂


  9. Hi! Im getting my first T soon, its a Black Brazilian T and i was wondering if coco coir was decent. I heard they like a dry substrate but im affraid if I use just coco coir it will be too fluffy and wouldn’t burrow. Maybe mix it with top soil? Idk have any suggestions? would appreciate 🙂

    Liked by 1 person

    • Hello! I currently have my sling on coco fiber, and it’s doing fine. Although the fluffy coco fiber doesn’t hold the greatest burrow, they WILL web up the inside of their burrows to reinforce them. If you want to add to it, top soil works great. Hope that helps!


  10. What brand of coco fiber do you use (10 lb brick)? And do you need to wash it more thoroughly since it isn’t Eco Earth? What size container would I need to make it all in?

    Thanks and keep up the great work man!


  11. And to add on to the other reply (sorry for not consolidating this into one), you said you put a 1/2” layer of vermiculite in all of your moisture living species enclosures right? Do you do this with your Phormictopus as well? I have a bunch of Pamphos and Phormics Id like to try this with.

    Thanks and sorry for asking for the obvious (I’m always paranoid and like to double check)


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s