So this is going to be kind of an unpopular opinion, but you don’t actually need charcoal for your terrarium! Yes, you read it right. Today I’m going to talk about why you don’t need charcoal for your terrarium. So if you’ve done any research into building terrariums, if you watch any videos, or read a blog post about this stuff, all of them tell you that you need to add charcoal to your terrarium either as a drainage layer or maybe as a separation layer between the drainage layer and your substrate. And it is my opinion that that is not actually necessary; you can avoid it if you want to. So let’s kind of walk through the details about why that is.
First, let’s talk about what charcoal is and what it does for your terrarium. Charcoal, sometimes called activated carbon, comes in two forms mainly. It could be either in the form of these black chunks of rocks or this black powder. Either one of those will be fine; they function the same way essentially. But basically, what it does is it binds to any toxins or chemicals that might be floating around, not just in a terrarium, but just in general. It’s used in industrial applications like wastewater treatment plants and pharmaceuticals. It’s used even in aquariums as a filtration mechanism to suck out all the chemicals and unwanted stuff that you might find in the water or in the air. And what adsorption is, is as chemicals pass through or get in contact with the charcoal, those little particles chemically bind to tiny microscopic pores that are on the activated carbon. Charcoal and activated carbon are really good at this because they have a whole bunch of these tiny pores all over the surface. They have a very high surface area with all those pores on them that are just waiting, ready to bind to any chemicals. And that’s what makes activated carbon so good at being a purification or filtration material, is its filtration properties.
So when it comes to a terrarium, the idea with activated carbon is that it’s supposed to suck out all the toxins and chemicals. These could be things like bacteria, nitrides, acetic acids, organic acids, and all sorts of stuff that could potentially harm your plants. The idea is, if you have activated carbon in your terrarium, it’s going to suck out those chemicals and toxins as the water passes through and gets in contact with that charcoal, and also sucks them out from the air directly. The idea is that’s supposed to help protect your plants, giving them cleaner air and cleaner water.
So that’s great and all, but that’s actually not a necessity for a terrarium. I’ve actually made a couple of terrariums myself and I haven’t used any activated carbon in them when I’ve put them together. And as far as I know, my terrariums are doing fine; I haven’t seen any problems with them. So just from my personal experience, you can add activated carbon to your terrarium, that’s great, but I just don’t think it’s really necessary. I think you can do just fine without having activated carbon in there.
One of the other big points that’s brought up about adding activated carbon to your terrarium is that the activated carbon and the charcoal, since they’re adsorption materials, those pores will actually get used up over time if enough toxins and chemicals have bound to the activated carbon. So if you think about it, while there are a lot of pores and binding surfaces on the charcoal, those pores will eventually get used up over time if you give it enough toxins and chemicals. So as those pores get used up, having bound to the chemicals, you can think about it like the chemicals and the molecules kind of clog those pores, preventing them from binding any further to additional toxins and molecules.
And so what happens in a terrarium is that over time, I’d say estimating about maybe a year or two, your activated carbon is actually going to lose its effectiveness. While it’s definitely going to work in the beginning, eventually it is going to run out and it’s not going to perform the filtration properties anymore. This is why in a lot of industrial applications, you’ll see they’ll actually have to replace the filter every so often because of this exact reason. The activated carbon loses its effectiveness because it has already bound to a whole bunch of chemicals. So that’s one of the reasons, probably the main reason, why I’m not really a fan of adding charcoal to a terrarium: it’s only temporary. It might give you some good filtration in the beginning, maybe for a year or so, but after that, it’s not really going to do too much for you and you’ll either have to replace it, which is going to be kind of a hassle, or you’ll just have to accept that you’re not getting the filtration properties. So if it’s going to run out anyway, then why put it in to begin with? And that’s kind of my thought process behind that.
Another point that I want to quickly mention here is that instead of activated carbon, you can actually rely on your moss to perform some of the filtration out there. What some people like to do is they’ll actually put sphagnum moss as the separation layer between the drainage layer and the substrate. What that does is sphagnum moss can actually absorb chemicals and heavy metals. There have been a couple of papers about that if you want to read more, but what people like to do, and what I recommend you do, is you can just put some moss into your terrarium and rely on that as your filtration and purification mechanism for your terrarium. That will help purify your terrarium without having to go out and buy a bag of charcoal.
So that’s pretty much why you don’t actually need activated carbon for a terrarium. It’s not really necessary; it can be helpful in the beginning, but eventually, it’s going to run out, and in my experience, most of the time your plants are going to be doing just fine without it. That’s pretty much all I have to share.