How to Make A Terrarium Without Charcoal

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Yes, you can make a terrarium without charcoal.

However, you’re more likely to encounter issues with mould and bad smells.


Many terrarium builders are opting to go without charcoal these days because charcoal isn’t having a significant enough impact on their terrarium to warrant buying it.

Why put charcoal in a terrarium?

The idea behind put charcoal in a terrarium is that it removes impurities from the soil and binds them to itself, so they can’t wreak havoc on your plants.

It’s basically a natural filter.

This makes sense – those of us with aquariums know that there’s often activated carbon in the filter medium to help remove impurities from the water.

I understand that. We’ve had aquariums for decades and charcoal is used to treat a variety of issues.

My issue is that I can see how the charcoal is filtering water – the water is pushed through the charcoal, on a regular basis. The water is always being filtered. I’m not sure how it would work in a terrarium where the substrate just sits there.

It does work for removing gases (and therefore bad smells), but it definitely has a shelf life. I’ve heard reports that activated carbon can be ‘full’ i.e. it’s bound as many toxins as it can hold in as soon as a month after it’s been added to a terrarium.

What can I use instead of charcoal in a terrarium?

Alternatives to charcoal:

  • Get a fan to improve airflow
  • Use springtails and isopods to keep the substrate from stagnating and to eat any rotten matter
isopod in terrarium
I caught him halfway through shedding his shell

Can I use regular charcoal for a terrarium?

I would stick to using activated charcoal because it’s the least likely to release nasties into your environment. Definitely don’t use anything that’s meant to be thrown on a barbeque, because it may have had chemicals added.

I use activated charcoal designed for aquariums because it tends to be ground pretty small. The smaller the pieces, the more surface area you get for your money, and the more toxins the charcoal can bind.

Where to put charcoal in a terrarium

Some people like a layer, so they put it above the drainage and below the soil. I tend to buy terrarium mixes with charcoal already mixed in, so if I were adding my own, I’d mix it with the soil before putting it in the terrarium.

I suppose it really just depends on your aesthetic – if you’re going for a layered look, add a layer, if not, mix it in. I can’t imagine that placement will have much of an impact on its effectiveness.

Can you make a terrarium with just soil?

Yes, but I wouldn’t recommend it.

We add a drainage layer for a few reasons, the most important being:

  1. When we water, any excess can drain into the bottom and won’t saturate the soil. That being said, having excess water sat in the bottom isn’t ideal, which is why I prefer to mist the soil rather than water it with a can. it’s better than having a layer of mud at the bottom anyway.
  2. Having a drainage layer of leca or gravel (I prefer leca, but it holds water so be extra careful about watering) provides airflow to the soil and stops it from compacting into a solid brick. Lack of airflow increases the amount of the anaerobic baceria that cause root rot.

Where to buy terrarium charcoal?

You can buy it on Amazon, or in your local aquarium shop or garden centre. If you’re using a ready-made terrarium soil, check the ingredients to check that there isn’t already charcoal mixed in.

Final thoughts

Charcoal seems to be one of those things that we just do, without considering whether or not it makes an actual difference.

I prefer to use a live ecosystem to keep mould and other nasties at bay, but I do understand people balking at the idea of having a glass box full of roly polys in the corner of their living room.

Add it if you want, but if you’re in the middle of making your terrarium and you realise that you’ve run out of charcoal I don’t think you need to worry too much about omitting it.

Caroline Cocker

Caroline is the founder and writer (and plant keeper) of Planet Houseplant

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