Terrarium Care 101: The Ultimate Guide to Terrarium Maintenance

This is a complete guide to caring for your closed, tropical terrarium.

I’ve been making and caring for terrariums for years, and I want to share my best practices for ensuring longevity and good health.

If you’re looking to build your own terrarium, I’d recommend taking a quick peek at our beginner's guide, which goes into even more detail on constructing the perfect terrarium.

In this article, I will assume you already have a terrarium ready-made, and I’ll focus primarily on care and common problems.

I will also answer your most frequently asked questions!

The ready-made live terrariums we offer include but are not limited to:

1. Mini Fittonia Terrarium 
2. Small and Standard Fittonia Terrarium
3. Large Fittonia Terrarium 
4. Ficus Terrarium 
5. Bottle Forest 
6. Cryptanthus Terrarium

If you're in a rush, here's a quick guide:

Quick Guide

1. What is a Closed Terrarium?
2. How to Care for a Closed Terrarium?
1. What Light Conditions Are Best for a Terrarium?
2. What Temperature Does a Terrarium Enjoy?
3. How Should You Water a Terrarium?
4. Should You Prune a Terrarium, Replant, or Let it Grow?
5. Glass Maintenance
6. Should You Fertilise Your Terrarium?
7. Microfauna
8. Should You Ventilate Your Terrarium?
3. Terrarium Care FAQs

Let’s get to it.

A terrarium made from one of our DIY kits

1 | What is a Closed Terrarium?

A true tropical terrarium is a self-sustaining ecosystem.

Water, nutrients, CO2, and O2 are cycled within a closed container allowing for continual growth over time with little human interference required.

Many closed terrariums also include microfauna such as springtails; detritivores that feed on decaying organic matter and produce nutrients for the plants in your ecosystem.

Houseplants, planters, and open terrariums, on the other hand, all require a closer eye kept on them.

Terrariums are a wonderful addition to any home or workspace and bring many benefits. And although they are notoriously low-maintenance, there are still care provisions you should be aware of.

2 | How to Care for a Closed Terrarium

Let’s start with the basics, shall we?

2.1 | What Light Conditions Are Best for a Terrarium?

Avoid keeping terrariums on your windowsill

Closed terrariums are made with tropical houseplants and thus enjoy bright but indirect light conditions.

If your terrariums receive too much direct sunlight, the plants may burn and dry out.

In the northern hemisphere, a north-facing window is perfect for achieving the right light conditions.

Terrariums can survive in lower light conditions, though they may not grow as quickly or retain their colour.

You can also use grow lights to provide light for your terrarium. I just recommend keeping your lights on a lower power setting to be safe.

2.2 | What Temperature Does a Terrarium Enjoy?

Light and temperature go hand-in-hand, as together they will determine exactly where you can position your terrarium.

Closed terrariums enjoy mild temperatures. I recommend avoiding temperatures above 10°C and below 30°C.

The ideal temperature range is around 15-24°C.

Truthfully, my terrariums have been subjected to lower and higher temperatures; this is just the best advice.

The real problem is rapidly fluctuating temperature.

Just follow these quick tips:

• Avoid placing your terrarium on a windowsill, even if it’s not receiving direct sunlight.
• Protect your terrarium from heating appliances such as radiators, computers, or space heaters.
• Keep your terrarium away from kitchen appliances that may produce high heat levels.

If you can see moisture in your substrate layers, you probably don't need to add more water. 

2.3 | How Often Should You Water a Terrarium?

The short and unsatisfying answer to this question is:

as often as it needs water.

That could be every month, every year, or every decade!

Terrariums notoriously retain water, so if you have a fully sealed terrarium, it should require little topping up.

However, now and again, you may need to give your tropical terrarium a gentle spritz.

Here are some signs that should tell you if your terrarium needs a drink:

• Dry Soil: The most obvious sign of underwatering is dry and crumbly soil. If the soil feels dry to the touch below the surface, it is likely that the plants are not receiving enough moisture. You can tell by its colour if you can’t reach your soil. If it’s especially light, it may be underwatered.
• Dry Moss: Moss is another great indicator. If your moss is dry or crispy to the touch, this is a sure sign that your terrarium lacks sufficient water.
• No Condensation: If there hasn’t been any condensation inside your container for weeks, it may mean the water cycle isn’t active and the terrarium needs a top-up.
• Wilting Plants: Plants that lack sufficient water might begin to wilt. Their leaves may droop, look limp, and feel soft instead of firm and perky, indicating they lack hydration.
• Brown, Dry Leaf Edges: When plants in your terrarium start to show brown and dry edges on their leaves, this is a clear sign of dehydration. The leaf tips and edges may appear crispy and could eventually curl.
• Slow Growth or Stunted Growth: If the plants seem to be growing very slowly or not at all, it could be due to a lack of water. Proper moisture is essential for healthy growth and development.
• Leaf Drop: An under-watered plant in a terrarium might begin to shed leaves prematurely. Older leaves might fall off first, but in severe cases, even newer leaves might drop.

I recommend using a mister when you need to water your terrarium. A mister will ensure a fine, even mist across the entire ecosystem while mitigating the risk of overwatering.

I always recommend avoiding pouring water into your terrarium, this is a sure-fire way to overwater your ecosystem.

I use distilled water to keep my terrariums hydrated, but you can use rainwater or reverse osmosis water too.

You can find water distillers on Amazon. This is the one we use.

Tap water often contains minerals that may be harmful to plants and moss over time. But if you can’t find anything else, tap water should be fine.

Is my terrarium overwatered?

Classic signs of overwatering include:

• Blackening leaves
• Mould build-up
• Constant, high levels of condensation
• Plants turning to mush
• Onset of fungus gnats

Overwatering is one of, if not the most common, mistake in maintaining a ready-made terrarium.

I always recommend erring on the side of less water if you’re unsure, and using a mister to hydrate your terrarium rather than pouring in water.

• Pro tip: If you think your terrarium has been overwatered, remove the lid and leave it off for a day or so to allow excess moisture to evaporate. Make sure to remove any dead/dying plants first.

One of our oldest terrariums that we are letting grow out, rather than pruning. 

2.4 | Should You Prune a Terrarium, Replant, or Let it Grow?

In all our terrariums, we carefully measure the nutrient balance so that they grow at a manageable rate.

They will grow, however, and you may need to prune your plants at some point.

You’ll be able to tell when this time has come because the plants will be near the top of your container or, in some cases, literally breaking out.

You have three options:

1. Let the terrarium do its thing. Let it grow!
2. Prune back your plants and reuse the cuttings.
3. Remove and replant the entire plant inside a new container.

Typically, I like to let my terrariums do their own thing. I quite like the ‘overgrown’ look (but this might also be me being lazy!).

However, if you want to clean up your ecosystem, I will usually recommend pruning rather than replanting.

This is because the plant has adapted to this environment and is enjoying it. Replanting entirely can risk shocking the plant, and you may lose your terrarium.

I recommend transplanting the entire plant if you have a Ficus terrarium, where the root ball makes it impossible for a simple pruning to suffice.

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A post shared by ome | Bring Nature Home (@ome.home)

How to prune a terrarium

Depending on the state of your terrarium, this may or may not be a significant job.

But don’t worry, I’m here to help. It’s never quite as bad as you think.

A terrarium tool kit will go a long way to helping you effectively prune a terrarium.

1. Use the tweezers to hold a stem in place, and with your other hand, trim your plants back one at a time.
2. If the plant has just one leaf atop a long stem, you should trim it at the very base of the stem.
3. If the plant has multiple leaves shooting off from the stem, you can select exactly where you would like to trim the plant back to. Trim just above the node each time (where the leaves separate from the stem)

• Pro tip: You can use your cuttings in a new terrarium! Pair pruning with the start of a new terrarium for the best results.

How to transplant a terrarium

This procedure is as straightforward as repotting a plant.

1. First, you must set up a new terrarium with a container adequately sized for your plant.
2. Gently remove the plant from its original container
3. Replant inside of your new container

That was easy.

Pro tip: See our beginner’s guide for a simple, step-by-step guide on making your own terrarium.

Infrequent glass dusting is recommended. Or frequent, depending on how dusty your house is...

2.5 | Glass Maintenance

The inside and outside of your terrarium glassware may need occasional maintenance.

Here’s a quick troubleshooting guide:

• Water spots: Water spots are caused by the build-up of minerals from tap water. The best way to avoid them is to avoid tap water. To remove them, wipe your glass clear using distilled water.
• Dust: If your glassware gathers much dust on its exterior, wipe it down with a cloth or kitchen towel.
• Condensation: Condensation is a sign of an active water cycle and, thus, a healthy terrarium. Don’t worry too much about condensation unless you think your ecosystem might be overwatered (see signs and care advice above)

2.6 | Should You Fertilise Your Terrarium?

All terrariums should come with some natural fertiliser.

All of ome’s terrariums include vermicast in the substrate (worm poo) that will slowly provide nutrients to the plants.

Mycelium in this medium will also break down decomposing organic matter (such as fallen leaves) over time and continue to feed your ecosystem.

Many terrariums also include microfaunae such as springtails and isopods – these custodial critters will clean up your clutter by feeding on waste matter.

They then return nutrients to your terrarium, taking the weight off your shoulders.

However, if your terrarium is experiencing particularly stunted growth and it doesn’t seem underwatered – you can consider using a diluted solution of organic fertiliser, which can be gently sprayed into your ecosystem.

Springtails. They're tiny, but powerful.

2.7 | Microfauna

If your terrarium has microfauna such as springtails or isopods, their populations will self-regulate depending on the available food sources.

They will feed primarily on any decaying wood or fallen leaves.

You can, however, top up their food supply as and when you like.

Find a patch of open soil and place in it some food. Be sparing, however, as too much can invite unwanted fungus gnats or mites.

You also want to avoid pouring any food onto plants and moss, as they can cause them to mould once decomposition begins.

Here are some of my go-to’s for microfauna meals:

• Nutritional yeast powder
• Uncooked white rice
• Cucumber slices
• Sterilised leaf litter

2.8 | Should You Ventilate Your Terrarium?

This is a contentious question.

I hear terrarium experts giving the opposite advice, so, things can get confusing.

Let’s break it down into true and false.

• “You should always periodically open and ventilate your terrarium for a few hours every couple of weeks”.

FALSE. I have many terrariums that are doing well and they have been closed for years. There is no set time frame for when a terrarium might need to be opened, just a there is no set time frame for when a terrarium might need to be watered.

• “You should never open a terrarium. Once it has been made, you should ‘set it and forget it’!”

FALSE. Although it may be the ideal, you cannot guarantee that a terrarium never needs to be opened. This may be for ventilation or another reason. Don’t set yourself hard boundaries when your terrarium might be in need of attention.

• “If you open a terrarium that has been going for years, it will die”

FALSE. I do think there is some merit to this. A successful terrarium that is still thriving is best left alone. But, you are not committing your ecosystem to a death sentence if you open it to have a sniff. Or a look, or whatever you’re doing.

• “Hermetically sealed terrariums may need to be opened for occasional ventilation, especially if the moss is yellowing”

TRUE. I have had Demijohn and Kilner jar terrariums suffer before, and I could only reason that the total hermetic seal caused the issue. Cork, on the other hand, is semi-permeable, and thus, some airflow is permitted.

“Ventilating your terrarium is helpful when you have mould building up”

TRUE. Although mould isn’t necessarily a sign of poor terrarium health, it can become a problem if left unchecked. Opening your terrarium can encourage new air to alleviate mould issues and allow excess moisture to evaporate.

In short – you may need to open your terrarium in the event there is an issue, but if your terrarium is fit and fine you should have no need.

But equally, there’s nothing wrong with opening up and taking a peak – if you want to!

A tiny spice jar terrarium - around 6 months unopened. 

3 | Terrarium Care Frequently Asked Questions

How often should I water my closed terrarium?

This will be based on various factors as and when your terrarium requires it. Signs for when your terrarium needs water include wilting leaves and dry, crumbly soil.

Do I need a mesh layer to separate my substrate layers?

I would argue that this is a myth, at least within the terrarium space.

Though a mesh layer won’t ‘hurt’ your terrarium (other than aesthetically) – it will provide no material benefit.

Your ‘layers’ don’t even truly need to be separate. They all form part of one substrate.

What is the best way to remove algae from terrarium glass?

Gently scrub the glass with a mix of water and white vinegar using a soft brush or cloth, avoiding the plants and soil. Try keeping your terrarium in a spot with less sunlight and investigate whether it may have been overwatered.

Why are my terrarium plants turning yellow?

Yellowing can be caused by overwatering, poor drainage, or lacking nutrients. Check moisture levels and adjust watering accordingly.

How do I add humidity to my open terrarium?

Misting can help increase humidity levels in an open terrarium.

Can I use tap water to water my terrarium?

It's best to use distilled or rainwater to avoid the build-up of minerals that can harm plants and cloud glass. But if you’re strapped, tap water should be ok.

What should I do if there's too much condensation in my closed terrarium?

Open the lid for a few hours to allow some moisture to escape. Remember, condensation is a good sign – the water cycle is active.

How can I tell if my terrarium is getting too much light?

If plants are bleaching, getting scorched tips, or the glass gets very hot, it may receive too much light. Move it to a location with indirect light.

What’s the best way to prune overgrown terrarium plants?

Use long scissors to trim back overgrown foliage, maintaining the desired shape and size. For a step-by-step guide, check out our pruning section in this article.

Why is there mold in my terrarium and how can I get rid of it?

Mould isn’t always a bad thing. Some mycelium in your substrate is healthy as it breaks down organic matter. But, excess moisture or unclean materials can lead to a build-up of mould. Remove the terrarium’s lid to allow for moisture evaporation and general ventilation. We do have a complete guide on tackling mould.

How do I deal with pests like gnats in my terrarium?

Use yellow sticky traps for adult gnats, and consider a diluted neem oil spray for the soil to disrupt the larvae. Place your sticky trap in place of the lid.

Can I place a terrarium in an air-conditioned room?

Yes, but ensure the terrarium isn’t in the direct path of cold air.

What are the signs that my terrarium is under-watered?

Signs include dry soil, wilting, and browning leaf tips.

How can I prevent root rot in a closed terrarium?

Err on the side of less water and follow our other care advice

Is it necessary to fertilize terrarium plants?

Generally, terrarium plants require little to no fertilizer. If needed, use a diluted, balanced, liquid fertilizer sparingly.

Why are my terrarium plants dying even though I follow all care instructions?

If you’re having persistent issues, please don't hesitate to contact us—we’ll be more than happy to help.

How can I safely introduce new plants into an established terrarium?

Before introduction, quarantine new plants for a few days, check for pests and diseases, and ensure they are suitable for the terrarium’s environment and have enough room.

What type of cleaning agent is safe for terrarium glass?

Use a diluted solution of water and vinegar. Avoid harsh chemicals that can harm the plants. Distilled water should generally be enough for the interior of your glass container, and isopropyl alcohol can be used on the exterior.

Can I decorate my terrarium with items from outside, like rocks and wood?

Yes, but sterilize these items in boiling water or bake them in an oven to kill harmful organisms before adding them to your terrarium.

How do I control the growth of fungi in a terrarium?

Reduce moisture levels, increase air circulation, and remove affected plant material promptly.

Is artificial lighting suitable for a terrarium?

Yes, especially LED or fluorescent lights that don’t emit much heat are suitable for providing sufficient light without the risk of overheating.

Why does my terrarium smell bad?

Odours can be a sign of decay or poor air circulation. Remove decaying plant matter and improve ventilation.

How do I adjust the terrarium environment for seasonal changes?

Monitor light and temperature changes with the seasons and adjust placement and watering as necessary.

What are the best terrarium tools?

Not to toot our own horn, but our toolset makes for a perfect companion in your terrarium maintenance endeavours.

What is the lifespan of a typical terrarium?

Proper care allows a terrarium to thrive for years, but plant lifespans vary widely. They may last up to a few months, or they could last a lifetime. Follow our care guides for the best chance at a long life.

Can terrariums help improve indoor air quality?

Yes, terrarium plants can help filter and purify the air, contributing to a healthier indoor environment. But – they’re sealed inside glassware so that they will have no effect on your room at large.

How often should I check my terrarium for maintenance needs?

Check weekly for signs of stress, pest issues, or water needs, and adjust your care routine as necessary based on your observations.

 

If you have any questions that aren’t answered here, just leave a comment below!

If you're looking for more care tips and design ideas, check out our Instagram. 

Until next time, folks.

- Joe