Turn An Aquarium Into A Terrarium: 9 Super Easy Steps!

One of the coolest ways to keep houseplants is in a terrarium. There are many advantages to this. 

Not only do they look amazing, they are often much easier to keep than the plants outside a terrarium, as there’s plenty of moisture and humidity to be had, rather than trying to get the plants to adapt to the dry air in our homes.

It also means that your plants are unlikely to suffer from pests or disease, as it’s an enclosed environment where you can fully control the growing conditions.

It’s a very satisfying hobby, and it doesn’t take a lot of work to make a terrarium look fantastic, or to keep it healthy.

Interested in making your own terrarium? Let’s get started.

Find Your Perfect Aquarium

Using an aquarium and repurposing it as a terrarium has many advantages over buying anything listed as a terrarium.

Aquariums come in lots of different sizes, and they tend to be cheaper than terrariums, especially if you get them second hand.

You might even strike lucky on a marketplace or in a thrift store, where an aquarium is likely to be a third of the original price, or even less.

They can also be much better quality than some terrariums that are on the cheaper side, and if you go for a larger aquarium, you’ll have a lot of room to play with when it comes to what plants you choose, and what design you might have in mind.

If you’re not sure what size to go with, aim for something that’s not tiny, but nothing huge. Something that will fit the space you have in mind.

As an alternative, you could even use a mason jar as a terrarium to get started, and move onto an aquarium. 

But largely, it is easier to start with something bigger, so that you have more room to play with, and you can spot any problems easier. 

When you’re looking for the right aquarium, it’s worth thinking about a lid, too. If you’re not planning on growing succulents or epiphytes in your terrarium, a lid is a must.

It keeps the environment stable, locking in the moisture and humidity, meaning that you can choose plants that love a lot of humidity instead of ones that like a drier environment.

Try to aim for a clear lid, so that you can position a grow light above it. This will make the plants grow upright, rather than leaning toward the light at an odd angle.

Once you have found the perfect aquarium, one of the first and most vital things you should do is clean it out thoroughly. 

No matter if it is brand-new or second hand, you want to start with a sanitized inside to avoid any issues, and very clear glass so that the light can penetrate properly.

If you can, set up your terrarium in its permanent place so that you don’t have to move it later. Once everything is in place, the terrarium can be very heavy!

Cover The Bottom With A Layer Of Gravel

As aquariums don’t have drainage holes (or, you hope not!), you need to add a substrate that will act as drainage, so the water has somewhere to go, and the soil is not constantly waterlogged.

So the first layer should be gravel. Aim for at least half an inch’s worth of gravel to cover the bottom of the aquarium, but you can go up to 2 inches if you prefer.

Try to make it as even as possible, but you don’t need to spend too long on it. This will give the terrarium a solid foundation for drainage.

Add Sphagnum Moss

Directly on top of the gravel, it’s a good idea to add a layer of sphagnum moss. The idea is that the soil will not sink into the gravel, and the water will drain away.

Make sure you get your sphagnum moss from a reputable, sustainable source. You won’t need a huge amount, but the good thing about sphagnum moss is that as long as it is shipped dry, you can store it for a while without having to worry about it.

Make sure to soak the sphagnum moss in warm water for a couple of minutes to rehydrate it. Ensure you wring out any excess water, and then spread a uniform layer of moss over the gravel.

It doesn’t need to be too thick, but it should be substantial enough that it supports the layers above.

Add A Layer Of Activated Charcoal

If you take a look at different guides on terrarium building, you may notice that some people recommend using activated charcoal, while others don’t think it’s worth it.

However, it’s useful to add a small layer of it on top of the sphagnum moss. The reason is that you want something to absorb any smells (terrariums, especially closed ones, can smell a bit swampy after a while).

It also acts as a water filter, and helps to prevent any fungi. Don’t go overboard – you don’t even need to bury the moss layer completely, but as long as it covers most of it, it will do its job.

Add Your Chosen Compost Mix

Now it’s time to add a suitable soil mixture for the plants you’re planning on growing in your terrarium. 

You could use a standard houseplant mix, or a general all purpose compost, but make sure you add one part perlite to help improve the drainage, and increase the oxygen in the soil.

While you might be tempted to make a smooth, even layer of compost, consider adding a gradient. 

This will make any design you have in mind look much more natural, and if you add more soil to the back instead of the front, you can create more interest, and create a gentle slope for any plants.

Make sure to water the soil when you’re finished adding this layer.

Time To Decorate!

Using a mixture of decorative and functional objects in your terrarium will go a long way in adding plenty of interest.

Consider A Backdrop

Some people like to put a background in the terrarium, not only to make the environment seem bigger than it actually is, but also to help climbing plants to have something to cling onto.

Chances are that with aquariums, you’ll be able to find a backdrop that fits. If not, most of them are made out of polystyrene, which means that you can cut it to size.

It also helps that it is lightweight. If you choose something else, make sure that it is not porous, like cork for example, as this will mean that it will rot in high humidity.

Driftwood

Another object that can make a huge difference to any terrarium is driftwood. It can serve several purposes: raising the height in random places, breaking up any straight lines or planting, provide support for climbing plants, and add some structural beauty to your terrarium. 

However, searching for driftwood can get expensive. But a good trick of finding driftwood suitable for your terrarium is to have a look in your local pet store, as they are bound to have some in the reptile section.

One of the key elements of terrarium design is to use natural materials where possible, and the more you can incorporate, the better your terrarium will look.

Stones: Create Paths, Make A Natural-Looking Landscape

Large or small rocks can create an impact in a terrarium, more than you might think. There are endless ways you can use rocks and stones in terrariums.

If you’re recreating a garden in miniature, for example, you might create some paths through your plants, or separate ‘rivers’ or ‘ponds’ or different planting zones.

Rocks can also add different textures and heights into a terrarium. 

You can match the type of rock to the look you’re going for: whether that’s smooth and polished, a rock that’s been worn smooth over hundreds of years in a riverbed, a trail of gravel, or an interesting and unusual piece of stone.

Install A Grow Light For The Plants

It’s important to give your plants a source of light. Terrariums should not be placed directly in front of a window that gets a lot of sunlight, as this can literally cook your plants.

If you want to place your terrarium on a bookshelf away from the windows, or on a dedicated table, it’s worth providing the terrarium with an artificial light source.

Don’t be tempted to try and give the plants enough light with a normal household bulb, as this won’t work for long, if at all.

You need a grow light that has been designed to give the plants the energy they need in order to thrive. 

It is much easier to set up a grow light before you put the plants in the terrarium, just leaving it off until you have finished planting.

There are many choices when it comes to grow lights. You can get different colors, too, but for a terrarium, white tends to work best. 

Purple can look very unnatural and harsh, ruining the hard work you’ve already put into your terrarium all at once! 

It can make a nice addition to a corner of your room that has a big plant in it, but stick to white grow lights for terrariums.

You should always go for a full spectrum grow light to mimic the sun’s rays. 

To make things easier, get one with a timer, or set up a timer plug at the socket so that you don’t have to worry about turning it on and off at certain times.

You can also get USB grow lights, which are handy if you don’t have a socket near where you want your terrarium to live, using a rechargeable power bank instead, but this can make things more complicated than they should be.

Depending on the shape of your terrarium, you may want to go for an overhead light, or one with its own stand that you can angle or even clip into place.

Always follow the manufacturer’s instructions when it comes to light placement. You want the grow light to be far enough away from the terrarium so that it doesn’t cause problems, but not too far that it can’t do its job. 

Introduce Your Plants To Their New Home

While it’s all been a bit technical up until this point, this is the part where everything starts coming together. 

But that’s assuming you’ve chosen what plants to use! 

It can be difficult to know where to start with what plants to choose for a terrarium. Luckily, it’s simpler than you might think, and it’s a good idea not to overcomplicate things for your first terrarium.

The only hard and fast rule is to choose plants that like the same or similar growing conditions. If you don’t do this, you will have some plants that will be very happy in the terrarium, and others will die rapidly.

There is also a section further down on some plant suggestions, if you want some ideas before you get started.

For an enclosed terrarium, stay away from succulents. They don’t tend to do well with enclosed and humid environments, as they need dry air and free-draining soil to thrive.

You can absolutely use them in a terrarium if you leave the lid off, being very careful not to overwater them. 

You’ll also need to keep the terrarium in as much light as possible to stop the succulents from stretching.

Enclosed terrariums are better suited to plants that like a lot of moisture and humidity. 

This does mean that you’ll be able to grow plants that love tropical environments, those that would be tricky to grow in a normal room in your home.

As you’ll be getting small plants too, they will also be cheap.

Tips On Planting Up Terrariums

Don’t be afraid to play around with different combinations of plants. You can use a mixture of very common plants and add a couple of rare ones. This will also help bring out the beauty in each plant you choose.

If you prefer, you could use only rarer plants, and see how they look together. Here are some tips to help you make your terrarium absolutely beautiful:

Use plants of different growth habits: at least one ground cover plant, a climber for the back of the terrarium, and one which will grow upright.

Arrange your plants so that the shortest is at the front of the terrarium, and the tallest one is at the back. 

Don’t be afraid to combine contrasting textures, sizes, and colors. Very finely-leaved plants (such as ferns) work well against bigger and leafier plants in different colors.

Apply the planting tips you’d use in a garden. Don’t plant in even numbers, use threes, fives, and sevens instead, for a less uniform look. 

You probably don’t want it to look so structured if you’re going for a naturalized look.

Lay out your plants on top of the soil and step back to see how they look, and adjust as you like.

Try to leave a good amount of space between each plant, allowing room for them to grow, as well as letting the air flow round each one. This will prevent problems later.

If you don’t want to do too much planting maintenance, choose slow-growing plants so that you won’t have to trim, divide, or split the plants very often. 

Plants To Consider Adding To A Terrarium

Fittonia

One of the most popular choices for any terrarium is fittonia, also called the nerve plant. These are gorgeous foliage plants which have prominent veins in their leaves, usually in shades of white, pink, or red.

As they love warmth, high levels of humidity and moisture, they are perfect for terrariums, and are easy to care for. 

There are many varieties to choose from, and they are readily available. 

Ferns

If you’ve tried growing ferns in your home before, but you’ve had no luck at all, watching with disappointment as they’ve gone completely brown and crispy, you might be tempted to steer clear altogether.

The good news is that ferns absolutely love terrariums, and if you’re trying to grow them inside, there is no better place for them than a terrarium.

They absolutely love humidity, warmth, and plenty of moisture, and terrariums provide this in bucket loads.

Most terrariums don’t look complete until you’ve added at least one fern, as they are absolutely beautiful, and there’s nothing quite like these plants when it comes to foliage.

There are many kinds of ferns to choose from. Pretty much any fern that you would grow as a houseplant will do well in a terrarium, but there are some other things to consider.

You can buy a larger indoor fern and divide it into several smaller ones (saving you some money while you are at it), or you can buy miniature ones that are already the right size. 

If your terrarium is on the smaller side, or you just don’t want to keep dividing ferns, you should go for a dwarf species (see also 20 Different Boston Ferns To Grow), such as the Dwarf Boston Fern (Nephrolepis exaltata), or the Lemon Button Fern (Nephrolepis cordifolia ‘Duffii’).

If you want something even smaller, a micro fern is the best option. They mainly act as ground cover, adding a good deal of texture into the floor of any terrarium. 

You might go for the Dragon Scale Fern (Pyrrosia piloselloides), or the Mini Asian Water Fern (Bolbitis heteroclita). 

Calatheas

Calatheas are another species of captivating plants that are worth considering for terrariums. 

It’s worth noting that while they can be tricky to grow as a houseplant – especially in drier environments where there isn’t a lot of humidity, ruining their gorgeous leaves – they do well in the warm, humid environment of a terrarium.

There are many types of calathea to choose from, and most are readily available as smaller plants, making them perfect for terrariums.

Begonias

You might be sensing a pattern here. If you’ve tried to grow begonias indoors and had no luck, you may be glad to know that these plants absolutely love the moist and warm conditions that terrariums offer.

Just be careful not to spray the leaves, as begonias absolutely hate this. Choose begonias that grow from rhizomes, also known as rhizomatous begonias. 

Not only are they easier to keep because the rhizomes act as an essential storage for water and nutrients the plants need, but also because they don’t need deep soil, making them perfect for terrariums.

One thing to remember is that begonias like compost that doesn’t hold onto water, so if you’ve followed the directions above, this should give the plant the drainage it needs.

It also helps that the leaves of a begonia are absolutely beautiful. 

Jewel Orchids

Naturally suited for terrariums, jewel orchids are forest floor plants that make a dramatic impact, with their gorgeous reflective leaves in lightning patterns.

They love plenty of humidity, which makes them perfect for an enclosed environment. They come in a range of shapes, sizes, and colors, but tend to stay fairly compact.

Shingling Plants

It’s worth adding a few climbers to your terrarium to vary the height levels, and one of the most interesting ways of doing that is to grow plants that ‘shingle’.

This means that the plants grow flat against a surface. You might try a Rhaphidophora cultivar (see also How To Grow Rhaphidophora Tetrasperma), or a climbing Ficus species. 

How To Keep A Stable Terrarium

As a terrarium is a living environment, it will change over time, and there are things you can do to ensure that it keeps thriving.

It will be more low-maintenance than keeping your plants in conventional pots, but you will still need to check on it now and then.

Keep A Vigilant Eye On It

This is the most important part, but it’s also fascinating to see how your terrarium changes. It’s worth keeping an eye on it, making sure that things are growing as they should, and that the balance between the moisture and plants is a good one.

Remove Any Dying Or Dead Plant Matter

This is a big one. Terrariums don’t usually have the insects and microorganisms to break down dead or dying organic matter like in the real world, so you should remove dead flowers or leaves as soon as you see them.

This also helps your terrarium look neat and tidy, too.

Keep An Eye On Moisture Levels

You’ll need to keep an eye on the moisture levels, making sure that the terrarium doesn’t get too dry or too wet for too long.

Some condensation building up on the glass is normal, especially on a sealed terrarium, but you don’t want too much moisture if you’re not going for a terrarium that recycles its own water.

Leave the lid open slightly, which allows air to circulate, stopping any diseases or too much condensation.

You will also need to top up the moisture levels occasionally, but always check before you water the soil. 

Allow the top inch of soil to dry out between watering, and this will help stop too much moisture from staying in the soil for too long.

Trim Back Plants Or Take Cuttings

You might be surprised at just how quickly some plants will grow in an enclosed environment, and how much they will love it. 

You may find yourself having to cut back plants on a regular basis to stop them overtaking the terrarium! 

You can divide them, too, but try to choose plants that won’t try to take over your terrarium completely, as this is more work in the long run.

Don’t Forget To Clean The Glass!

This is especially important when condensation forms on the inside, and dust on the outside. 

For the healthiest plants possible, always keep the glass clean, as this allows as much light as possible to get to the plants, which will also stop any fungal problems.

Final Thoughts

Terrariums are a great way to keep plants that you might otherwise struggle to grow indoors. It keeps the environment warm, humid, and just as importantly, stable, allowing the plants to thrive.

It’s also interesting to see how your terrarium changes over time, allowing you to understand the plants better,  and you will soon be able to tell exactly what they need just by their appearance.

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