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You only really need three things to make a terrarium: a container, substrate, and plants.
Buuut…you can really expand your options if you add a few more items to your list.
Like every hobby I’ve ever had, I like to start with the very basics, and not buy anything for a couple of months, just in case it was a hyper fixation rather than a long-term hobby.
(btw this goes against every instinct in my body, which is to go out and buy EVERYTHING ever associated with the topic – I try to curb this impulse by watching every YouTube video I can find on the subject so I can fixate for free).
Building a terrarium is one of those things that you can totally adapt to your space and budget. Here’s mine:
I appreciate that this is a terrible photo BUT the light’s on a timer and I don’t know how/ didn’t want to override the settings so it’s mostly a picture of my reflection. NEVER MIND.
This terrarium has lights, a heat mat, a fungus-eating team, and a tonne of plants.
Terrariums don’t need to have this stuff. But they can also have a lot more stuff (like fogger, which look really cool).
We also have a frog in there, who was a rescue we happened upon. You also don’t need a frog. He lives in a seed pod so we rarely see him, but we can hear him shouting at night.
If you’re a beginner, you may want to start with something pretty basic. Fundamentally, all terrariums start with the same basic equipment if you want it to work properly and not just rot, such as:
A terrarium
You can use anything, as long as it lets the light in. I also like to have a bit of airflow, but sealed terrariums are also a thing. My terrarium is an old aquarium, so we have a little fan attached to the little hatch through which you would usually feed the fish. I would recommend having a bit of airflow if you’re a beginner. You don’t need a fan, just a lid you can take of or something, because getting the humidity and plants right can be tricky in a sealed terrarium. You don’t want to end up with a load of smelly mush mixed with algae.
You could use an old glass jar, cloche, or buy a purpose-built terrarium. Old aquariums are also pretty cheap from places like Facebook marketplace, and you don’t need to worry about it being able to hold water.
Clean it out thoroughly before using it. Terrariums don’t need to be sterile environments, but you don’t want algae or anything in there before you start.
Washing up liquid and white vinegar are pretty good for getting rid of any streaks.
If you decide to get a light for your terrarium, streaks will drive you mad, so it’s weirdly important!
Gravel/LECA
You need something for the excess water to drain into. We use leca (you can see the layer in the picture above) because it absorbs excess water from the substrate. You could use gravel, but that doesn’t absorb water.
It may seem more cost-effective to use gravel, but it’s potentially a short-term hack. If you overwater, the gravel won’t absorb any moisture, and there’s not sufficient gravity for the water to drip out of the soil.
Excess water will go into the gravel, but unless you’re seriously overwatering, it’ll just sit there and stagnate. It’s not dangerous but it is gross.
The substrate will stay waterlogged for literally months (due to the humid environment in the terrarium) and your plants will rot.
Activated charcoal
I have an article on activated charcoal here, if you want to read up on why it’s so important, but basically, it binds impurities in the soil to itself and effectively removes them. I use it in my potting mix, but if I don’t have any, it’s not that big of a deal. I wouldn’t, however, recommend leaving them out of my terrarium mix. Either mix it into your substrate, or put a layer above the leca.
Terrarium substrate
In the picture of my terrarium above you can see a white barrier between the leca and the substrate. It’s just fish tank filter padding and it just keeps the soil from falling into the leca and looking gross. You can get carbon-infused ones too, though I’ve not tried those myself.
I bought a terrarium substrate, rather than making my own. I don’t change the substrate, so it didn’t seem cost-effective to buy the separate components and make my own.
I don’t know if you’re meant to change the substrate, but we have a bio-active terrarium (we put bugs and plant matter in to keep it as natural as possible) so we don’t need to worry about nutrients depleting in the soil. If you don’t have creatures in your terrarium, you can just fertilise the plants like you would a regular potted plant.
Plants
Do your research on plants and make sure you get ones that will do well in a terrarium. Succulents and air plants are likely to just rot, so get something more tropical.
I have a whole article on terrarium-suitable plants, but small specimens of aglaonema, calathea, pothos, and ferns will do well.
My terrarium has a rhapidophora tetrasperma (which is rapidly outgrowing the space, but the leaves are HUGE), a heartleaf philodendron (same), a Calathea Beauty Star and Velvet Touch (both throwing out two new leaves apiece atm), a begonia amphioxis that keeps getting buried in the leaf litter so we’ll probs lose that one), a pink agloanema that looks amazing, a Philodendron squamiferum that looks awful, and a Marble queen pothos that grow so quickly you can practically see it.
A terrarium is a great environment for these plants because the humidity, light, and substrate are perfect for them. I’m gonna feel really sorry when they have to be taken out and potted up in the outside world. It’s not gonna be nearly as nice for them.
A spray bottle
One of the things I really love about terrariums is that you don’t have to water them. Instead, we just mist ours. I know that I’m against misting in general, but it’s the perfect way to keep the soil damp without soaking it. Since it’s a closed environment (but not sealed), the soil doesn’t dry out, but it doesn’t get saturated either.
My boyfriend sprays the terrarium twice a day, which…is a lot, but we kind of treat it like a pet and spray it when we feed the rabbits (they’re all in the living room).
Some plants will not like being sprayed, but it’s a bit of trial and error. The Squamiferum doesn’t like it at all, and we had a maidenhair fern that went brown, I think due to the praying. It was still growing like a weed, and it didn’t shrivel like they do when they’re thirsty, so I can only think that it was the spraying.
Weirdly, the Calathea seem to love it!*
*I say weirdly only because Calathea never seem to love anything.
Dechlorinator
We make sure to always use dechlorinated water in the spray bottle (we use this one because we use it in our aquaria, but you can use a cheaper one if you’d prefer) because if anything going to harm the leaves, it’ll probably be chlorine.
It’s not strictly necessary (unless, like us, you have critters in your terrarium), but it could save you some leaf browning.
Beneficial bugs
Again, not strictly necessary, especially if you have a small aquarium and plan on using a fertiliser, but we prefer a more natural approach. We have both springtails and isopods, but you could just use springtails if you’d rather.
Springtails eat any rotten, decaying matter, and are a great way to clean the terrarium clean without having to actually clean it. As far as I’m aware, they don’t try to escape (unlike the flies we feed the frog), and they’re pretty cute!
Lighting
You don’t NEED a light for your terrarium, but it will not only help your plants to grow, but it’ll make your terrarium look more like decor than a weird box of plants.
We put a grow light in the old aquarium light fitting, but you could just stand a lamp over it (with a grow light bulb in it) if you’d prefer. You could also clip grow lights inside.
I wouldn’t recommend any adhesive things such as Command strips, just because the high humidity in the terrarium could compromise the glue. We tend to go for less high-tech solutions (zip ties. It’s always zip ties).
Heat mat
Again, not imperative (unless you have a frog) but it can really get your plants growing. If you have a large terrarium with a light and a heat mat, you’ve created the perfect propagation or rehab box, so consider lights ad heat pads an investment if you spend a lot on plants, or sell cuttings.
We just got a cheap one from Amazon and hooked it up to a timer thing that will cut out once the right temperature is reached.