ABG Mix – The Classic Terrarium Substrate (+ Recipe)

ABG mix has been the gold standard in the terrarium and vivarium industry for many years.

First developed by – and named after – the Atlanta Botanical Gardens, it’s a tried-and-tested option that brings a lot of benefits to the table. 

I’ve personally used variations of this classic mix in a wide variety of terrariums with (mostly) great success. So, in this article, we’re going to break down the components that make this mix so special and effective.

Plus, we’ll share the ABG mix recipe so you can make your own!


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Why is the ABG Mix so Good?

For starters, substrate mixes are almost always superior to single substrate choices.

Each element of the mix plays a different role in supporting plants and facilitating a healthy terrarium ecosystem. The ABG mix is particularly effective because it balances each of those elements so well.

  • Excellent drainage – In a closed system, drainage is essential to keep your plant’s roots healthy and aerated (and not drowning in a soggy substrate).
  • Great water retention – Ensuring your water-loving plants are well supplied, and it also helps to boost humidity to create that tropical environment.
  • Retains nutrients – Though the peat moss doesn’t add much in the way of nutrients, it’s incredibly effective at holding onto them.
  • Resists compaction – With so much spongy, fibrous material in the mix, it’s able to stay well aerated and resist compaction over time.
  • Long lasting – This mix can easily last years before losing functionality.
abg mix substrate in a bowl
Light and fluffy is the name of the game with this ABG mix.

Classic ABG Mix Recipe

Surprisingly, it’s actually quite difficult to find the source citation for the ABG mix recipe.

And if you ask any expert what it was, you’re likely to receive a slightly different answer! Though based on my research, it seems the original recipe was as follows:

  1. Sphagnum Moss – 1 part
  2. Tree Fern Fiber – 2 parts
  3. Orchid Bark – 2 parts
  4. Peat Moss – 1 part
  5. Charcoal – 1 part

Putting this recipe into practice, I believe these ratios are set in volume rather than weight, as weight can vary a lot depending on the material.

And though this is the original recipe, you’ll now see many variations available on the market. So don’t be surprised if the materials list of a purchased pre-made mix doesn’t match this exactly.

So, in the rest of this article, we’re going to deep dive into these materials and show you how to substitute them where necessary.

👉 Or, if you want to grab a bag of classic ABG Mix, here’s one on Etsy.

ABG Mix Components

ABG mix is actually classed as a soilless substrate.

Despite using traditionally fibrous and chunky base ingredients, the mix is designed to be quite light and fluffy (and it pulls it off).

This is partly thanks to the addition of several materials chosen for that very purpose but also due to each of the materials being used at a loose, fine granularity.

It’s designed to mimic the native tropical soil layer of the rainforest environment, so it’s an ideal substrate for bioactive vivariums and terrariums.

So, if you’re making this mix yourself, it’s important to get the right kinds of ingredients to get the ideal consistency.

1. Milled Sphagnum Moss

Of course sphagnum moss features in this list; it’s a true terrarium staple.

It’s fantastic at retaining moisture and boosting humidity, and it helps to create an acid environment that slows the rate of decay.

You’ll typically see “milled” sphagnum moss listed in the recipe, and it’s essentially just sphagnum that’s been ground down to a fine grain.

If you can’t find it at this consistency, I’ve seen forum users recommend just throwing the long-fiber sphagnum moss in a blender or chopping it up with a knife.

In my build for the Essential Guide to Tropical Terrariums – I just ripped it up a bit with my fingers!

dried sphagnum moss fibers
Long-fibre sphagnum moss is super easy to source and shred yourself. I’d recommend you do that.

👉 Shop sphagnum moss on Etsy.

2. Tree Fern Fiber

Sourced from a variety of tree fern species (often Dicksonia), this versatile material looks like heaps of tiny twigs and really adds an element of natural aesthetic to a mix.

Tree fern fiber is primarily there for aerating the substrate and providing drainage.

The twig-like shapes form irregular frameworks in the mix, supporting the overall structure, resisting compaction, and creating air pockets.

tree fern fiber
Tree fern fiber is pretty good stuff, though it can be hard to find a good/sustainable source.

👉 Shop tree fern fiber on Etsy.

3. Orchid Bark

Orchid bark (named for what it’s used for, not where it comes from) serves a similar purpose to the tree fern fiber in providing drainage and aeration.

The material comes in a variety of degrees of “chunkiness” depending on how it’s processed and what trees it’s sourced from (fir bark being the most commonly used).

Ideally, you’ll probably want to find orchid bark at the smallest possible particle size.

orchid bark chunks
This orchid bark is a relatively small grade that’s suitable for most terrariums.

👉 Shop orchid bark on Etsy.

4. Peat Moss

Peat moss is a more controversial substrate element.

It’s often confused with sphagnum moss because, in many ways, they come from the same peat bog source (and kind of share the same name), but they’re very different things.

Peat moss is typically included for its excellent water retention and uniquely powerful ability to retain nutrients. Plus, it has a nice fine texture that’s good for planting in.

But sadly, it’s a non-renewable product, so it’s getting less use over time (we don’t personally use it for this reason).

I prefer to use coco coir, as explained later in the “Substitutes” section.

5. Charcoal

Charcoal is often used in terrariums for its ability to filter any water that passes through it, thus “sweetening” the substrate.

Due to its porosity, it can also help with water retention and aeration too.

Though the recipe doesn’t indicate any one particular kind, horticultural charcoal and activated charcoal are your best bets from a filtration point of view.

Being the most porous of all (by a large margin), activated charcoal is arguably the most functional, but it’s also the most expensive. Horticultural charcoal sits somewhere in the middle as a happy medium.

Just note not all types of charcoal are suitable for terrariums – so it’s important to choose the right kind. Check out my guide to terrarium charcoal for more help.

horticultural charcoal chunks
Horticultural charcoal will need smashing up before adding in.

👉 Shop activated charcoal on Etsy.

Adapting the ABG Mix – Material Substitutes

With any good substrate mix, the sum is greater than its parts

Each element plays an important role, but the interaction between them is critical to success too.

In this case, consider how the tree fern fiber framework might support the chunkier bark pieces and finer fibrous elements. We can begin to see why this mix is so effective at aeration and drainage.

That’s why adapting a mix isn’t always quite as simple as it may seem.

However, with a variety of the original recipe ingredients being either expensive, hard to find, or unsustainable, it’s worth exploring ways to do it.

I always recommend ABG mix as a starting point, but I’ve never actually used the original recipe.

Tropical substrate up close
Here’s my take on an ABG-like substrate mix.

For me, peat moss is a definitive no, and tree fern fiber is too difficult to source sustainably (or at least without spending a fortune). Plus, as good as the ABG mix is, it can always be fine-tuned to better serve your desired setup.

So shall we jump to my recommended material substitutes?

*Wait, hold up. I just want to make one thing clear before I’m flamed into oblivion. These are not 1-1 replacements, and they do fundamentally change the mix as a whole.

 I’m not saying these substations are perfect, but they’re the best fits that I can think of – so let’s see them.

Peat Moss -> Coconut Coir

With excellent water retention properties, coconut coir can be a good substitute for peat moss.

Peat moss decays over time, which on one hand, is a good thing as it releases nitrogen into the substrate (which can help support plant growth). But, on the other hand, you have an organic component that is eventually going to fully break down and spoil (normally in a few years).

Coconut coir overcomes this as it’s a completely inert, very stable material. So it won’t degrade for a very long time, but nor will it support plant growth in any way.

coco coir in terrarium
As far as substitutes go, this is the material most like its original, and I much prefer it.

👉 Shop coco coir on Etsy.

Tree Fern Fiber -> Pumice or Lava Rock

Tree fern fiber is often the most difficult component to source and, frustratingly, the most difficult to accurately replace.

Though pumice and lava rock are both completely different in appearance and structure from tree fern fiber, they’re also very effective at adding aeration substrate and improving drainage.

So, even though it’s going to significantly change the consistency of the mix (rocks and twigs are very different things), they’re arguably the most capable substitutes for performing the function of tree fern fiber.

crushed lava rock chunks
This crushed lava rock is my go-to material.

Over to You

Do you use ABG mix in your terrariums or vivariums? I’d love to hear from you!

Particularly if you’ve substituted any ingredients or come up with your own recipe.

About The Author

20 thoughts on “ABG Mix – The Classic Terrarium Substrate (+ Recipe)”

  1. This has a ton of great information. That being said, cococoir (or cocofiber) is definitely NOT ‘inorganic’. It may resist degradation for longer, but saying that it is inorganic (like vermiculite is) weakens the validity of the rest of this wonderful information.

    1. Thanks Aaron, you make a very fair point 😊 By inorganic I was thinking more from a chemistry point of view (in that it’s not supplying any organic compounds) but as it comes from a biological source (and it will eventually break down) then you’re absolutely right, it’s wrong to call it inorganic. I’ve updated the article with your comments in mind, and I really appreciate your kind words.

  2. Thank you for your helpful information! I still have one question regarding this recipe. Is this recipe suitable for growing trees? From my understanding, all these materials are quite light in weight. Are this mix able to provide enough physical support for a small fruit tree (for example a dwarf mango tree)?

    1. I can’t say for sure but you’re absolutely right, it’s quite a lightweight fluffy mix. I’d imagine you would need something heavier to support a tree.

  3. Thanks for all these details! I have only 1 question: what type of peat do you mean? The one which has higher acidity and little nutrients (from boglands), or the one which is Ph-neutral and has more nutrients (from fens). We have both in market.

  4. Is it possible to substitute vermiculite for perlite? I have plain vermiculite for gardening, but the perlite available all has MiracleGro mixed in…not good for reptiles.

  5. Hello and thank you for some very interesting and valuable information. I grow orchids so that’s why I found this article of interest. Coir as being a slowly decomposing organic material has already been covered. As a substitute for orchid/pine bark I’d recommend the use of coconut husk chips (CHC). It has the similar decomposition quality of coir but retains far more moisture than bark. But if mixed with LECA pellets it can cut down on the overall amount of retained water, distributing moisture more evenly and still imparting light weight and compaction resistance while being inorganic and totally resistant to decomposition. The only thing I would also like to point out is that while both petite and vermiculite are both inorganic, vermiculite does hold more moisture than perlite, so they are not completely interchangeable in my opinion. But I believe that all these various products can and should be considered in formulating the ideal terrarium or terrestrial orchid potting media mix depending upon your individual goals and environmental conditions.

    1. In some ways, yes. Tree fern fiber is the hardest to replace because it has quite a unique physical structure. Though, sand is still effective at substrate aeration and drainage.

  6. As someone else mentioned, while similar, perlite and vermiculite are not really interchangeable. Vermiculite will absorb more and has a higher gas exchange making it a more damp substrate.

    While I would prefer to use an all natural substrate, I am beginning to feel using something like plastic twigs would be the most comparable to tree fern fiber.

    1. I totally agree (I’ve just noticed and updated my original comment that others have referred to). We’re all learning! 🙂

  7. I am attempting my first bioactive build, ideally for a crested gecko down the line once everything is established. When making this substrate do you layer or mix all together? I’ve worked out everything else in the terrarium except the base so far and that seems to be where I’m running in to trouble.

  8. Is mixing parts based on weight, or volume? Sphagnum moss is very light and fluffy so based on weight, it takes up a huge amount of space compared to volume. Thank you!

  9. How good would this mix be for general houseplant use? I’m building up a pretty good collection of tropical houseplants and am looking for the best, all around substrate to pot them in.

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