Activated Charcoal in Terrariums: Debunking the Myth

Terrariums, those miniature indoor gardens, have once again captured the imagination of gardening enthusiasts. However, it seems that misinformation about terrarium care has also made a comeback, particularly concerning the use of activated charcoal in the soil. Let’s explore the truth behind this seemingly popular soil additive and unveil the real secrets to thriving terrariums.

The Charcoal Conundrum

Activated charcoal, often touted as a miracle ingredient for terrariums, supposedly keeps the soil fresh, removes toxins, controls bacteria and fungus, and even maintains a refreshing scent. But do these claims really hold water? Let’s examine them closely.

Fresh Soil Fallacy

What does it even mean to keep the soil fresh? While the term may sound appealing, it lacks clarity. Moreover, activated charcoal’s ability to absorb toxins is limited. Given that terrariums require less water and fertilizer compared to other gardening methods, the presence of significant toxins becomes questionable. The few toxins that do exist are likely to break down naturally, providing essential elements for plant growth.

Microbial Misconceptions

Bacteria and fungus may not be deterred by a piece of activated charcoal. In fact, they may even settle on it and gradually decompose it. If these microorganisms find the conditions near the charcoal unfavorable, they can simply move away. In this regard, activated charcoal does little to combat the presence of bacteria and fungus in a terrarium.

Garden Myth: Do You Really Need Activated Charcoal in Terrariums?
There is no need for a layer of activated charcoal in a terrarium (nor for a drainage layer of rocks, but that’s another story!) Read Easy Terrarium Care for more on that! Photo:

The Charcoal Advocate

Some sources insist on adding a layer of activated charcoal at the bottom of terrariums but fail to provide any substantial evidence supporting this practice. One might wonder whether these sources have a vested interest in promoting the activated charcoal industry.

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Water Less, Excel More

The negative effects commonly associated with terrariums, such as harmful fungi, bacteria, and unpleasant odors, can typically be traced back to one culprit: overwatering. The key to successful terrarium care lies in watering sparingly. Only water the terrarium when the soil starts to dry out, and even then, use small amounts of water. By following this simple rule, you can avoid most of the common pitfalls that jeopardize the health of your terrarium.

The Lightening Effect

One positive quality of activated charcoal is its ability to increase aeration in the growing mix. However, other cost-effective alternatives like perlite and vermiculite often already exist in the potting mix you initially purchased. Unless you overwater your terrarium, these components provide adequate airspace. If you feel the need for enhanced aeration, adding more perlite or vermiculite should suffice.

Garden Myth: Do You Really Need Activated Charcoal in Terrariums?

The Proof is in the Pudding

To date, there has been no extensive scientific study examining the true impact of activated charcoal in terrariums. It is highly likely that researchers find the concept too trivial to warrant serious investigation. However, thousands of successful terrariums have been created without the inclusion of activated charcoal, firmly disproving its necessity.

Garden Myth: Do You Really Need Activated Charcoal in Terrariums?
David Latimer’s 50+ year old terrarium contains no charcoal. Photo:

As someone who used to make terrariums professionally, I initially believed in the hype surrounding activated charcoal. However, after consulting with fellow terrarium enthusiasts, I conducted an experiment. I created identical terrariums, with and without activated charcoal, and observed no discernible differences in their performance, even after a year of careful observation. I even maintained charcoal-free terrariums for more than five years without any negative consequences. The oldest known terrarium, over 50 years old, continues to thrive despite the absence of activated charcoal during its creation.

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So, before you succumb to the allure of activated charcoal, ask yourself: Where is the concrete evidence of its indispensable role in terrariums? The truth is, it simply does not exist. Opt for proper watering practices and focus on creating a well-balanced terrarium environment. Your green oasis will flourish without relying on this controversial soil amendment.

For further guidance and inspiration, visit Ames Farm Center for a wide selection of terrarium supplies and expert advice.