Terrariums are beautiful little indoor gardens that allow you to appreciate nature up close. But their warm, humid conditions also make them prone to mold growth. While a small amount of mold is normal, too much can ruin your terrarium.
In this guide, we’ll explore the most effective ways to prevent mold in terrariums so you can enjoy healthy plants and gardens.
What Causes Mold in Terrariums?
Mold is a fungus that thrives in moist environments with decaying organic matter – exactly what a terrarium provides! Here’s why they easily grow mold
- High humidity from the enclosed space and frequent misting
- Presence of soil, leaf litter, and dead plant parts
- Stagnant, poor air circulation
- Overwatering leading to a soggy substrate
- Mold spores in the air landing on damp surfaces
Just a few spores can start a rapidly growing mold colony. While some mold is normal, too much can smother plants and make terrariums look bad. Prevention is key to control mold.
10 Ways to Prevent Mold Growth
Here are the top 10 methods to deter mold growth before it becomes an issue:
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Use Activated Charcoal – Absorbs toxins and chemicals that encourage mold Add a layer above drainage or mix into substrate Also removes odors and clarifies water.
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Increase Air Circulation – Stagnant air promotes mold. Open terrariums or add small fans to improve air flow.
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Control Watering – Overwatering causes soggy soil, the perfect home for mold. Allow the soil to partially dry out between waterings.
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Use Distilled Water – Tap water has minerals and contaminants that can increase mold growth. Distilled, filtered or rain water is cleaner.
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Sterilize Hardscape Items – Boil or bake any driftwood, rocks, bark or other hardscape elements before adding to terrariums. This kills any spores present.
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Introduce Springtails – These tiny insects eat mold and help control populations. Their waste also fertilizes plants!
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Apply Cinnamon Powder – Dusting cinnamon on the soil and hardscape can inhibit mold growth thanks to its natural antifungal properties.
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Improve Drainage – A drainage layer of gravel, LECA or charcoal covered with mesh prevents wet soil. Good drainage deters mold.
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Bake the Soil – Heating potting mix at 200°F for 30 minutes kills any mold spores present before use.
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Let New Terrariums Sit – Allow newly assembled terrariums to sit open for 1-2 weeks. This dry period prevents initial mold blooms.
What to Do If Mold Occurs
If despite preventative measures mold still develops, take action to control it:
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Allow more drying time between waterings and increase air circulation.
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Spot treat visible mold with diluted hydrogen peroxide or alcohol on a cotton swab.
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Remove badly affected leaves and prune back moldy plants.
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Use a turkey baster to remove excess water pooled in the drainage layer.
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Apply cinnamon powder or chamomile tea spray to inhibit further mold growth.
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Introduce springtails to eat mold and keep it under control.
Be Patient and Persistent Against Mold
Don’t get discouraged if some mold occurs – early intervention and persistently addressing contributing factors will bring terrarium mold under control.
With proper watering, air flow, clean materials, and beneficial creatures like springtails, you can achieve a balanced terrarium ecosystem that minimizes mold.
While you can’t avoid all mold, you can reduce it to enjoy healthy plants and beautiful miniature gardens. With a little patience and these handy tips, you’ll be mold-free in no time!
Bake Your Soil
As we work our way through the layers of your terrarium, you’ll realise there’s a little something you can do at every stage.
Each layer serves a function, and your substrate’s provision of nutrition is arguably the most vital for a plant-based closed terrarium.
I found out the hard way that no matter where you get your soil from, there is no guarantee there won’t be dormant spores laying in wait for some water.
Again, this is typically only an issue when using soil taken straight from the outdoors or cheaper stuff bought online.
One way to assure your soil is safe is to sterilise it just as you would a sturdy glass vessel.
Let’s take a look at some of the best ways to de-fungi your substrate layer.
- In the oven: Probably the most conventional way to clean your soil, baking is quick and easy to do for significant quantities of the brown stuff.
- Crank your oven up to 180-200F / 82-83 C, lay your soil in an oven-proof dish and cover with a layer of foil. Leave to bake for 30 minutes, then remove and allow cooling.
- Don’t allow the temperature to exceed the recommendation as any higher could produce toxins, and we don’t want that.
- In the microwave: When dealing with smaller amounts of soil the microwave is another easy option.
- Make sure to use microwave-safe containers (NO FOIL!) with some room for aeration. For every 0.45kg (1 pound) of soil, heat it up for 45 seconds. Again, leave to cool until use.
Tips:
- There is also an option to steam your soil in a pressure cooker, but if the substrate mix is high in nitrates there’s a chance of combustion. Therefore, I will NOT be recommending this method
- Depending on your substrate you MUST research your substrate type and its needs before baking.
- Aquarium soil, for example, does not need to be sterilised.
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4 | Preventative Measures
It’s the same as if you were going to make your own hot sauce or jam, do not assume that your glassware is pristine clean no matter where you’ve got it from.
Residual bacteria or fungal spores can reside within your vessels – so it’s important to clean them first.
There are two ways of doing this, and which method you choose really depends on the glassware you’re handling.
The Ol Rinsenwipe
- Hot soapy water + a sponge. Grab some rubber gloves and get scrubbing.
- Make sure you wipe down the inside and out.
- If you’ve got an awkwardly shaped vessel that’s hard to scrub; try letting the hot water sit inside the terrarium for 10 minutes, then rinse it out until all the bubbles have disappeared.
Deep Heat
- Whack on the oven to around 275 F / 130 C. If you have a sturdy, thick glassed container (think mason jars or demijohns) sticking it in the oven is the most effective way to sterilise your glassware.
- The high heat will eradicate any unwanted inhabitants.
Pro Tips:
- You want the vessel to heat for at least 30 minutes
- Use oven gloves when removing the vessel from the oven
- If you’re sterilising multiple containers at once, do not let them touch each other
- Only put the glass elements of your vessel inside the oven
- Do not rinse hot glass with cold water!
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HOW TO STOP MOLD GROWING IN A TERRARIUM, PALUDARIUM, VIVARIUM
FAQ
How to avoid mold in a terrarium?
Is mold normal in a bioactive terrarium?
Mold is generally harmless in small doses, but too much of it often indicates a problem in the balance of your vivarium’s “ecosystem.” To help keep your vivarium in balance, ensure good airflow, make sure your substrate drains well, and don’t let things get too wet.
How do you stop mold from growing inside?
- Keep the indoor humidity below 60% relative humidity, ideally between 30% and 50%.
- Repair leaky pipes and faucets.
- Turn on the exhaust fans when bathing and cooking.
- Clean out the gutters.
- Make sure water drains away from your home.
How to prevent mold in substrate?
- Optimize watering : Reduce the amount of water during the winter months when plants often enter a period of dormancy. …
- Improve air circulation : …
- Remove the mold coating : …
- Use fungicides : …
- Transplantation : …
- Increase the light :
How do I prevent terrarium mold?
Prevent Terrarium Mold with the Following Guidelines: Use Clean and Sterilized Soil: Mold can thrive in contaminated soil. Therefore, opt for clean and sterilized soil when planting in your terrarium to mitigate mold growth.
Why is my terrarium moldy?
A closed environment, poor ventilation, and excess water provide ideal conditions for mold growth. Overwatering: Overwatering is a direct cause of high humidity in the terrarium. Lack of light: Light plays a crucial role in the process of photosynthesis, helping plants grow healthily and limiting mold growth.
Can you get a moldy terrarium with healthy plants?
However, you can still get a moldy terrarium with healthy plants. Molds feed on sugars and other moist organic matter. They can even feed on surfaces like plastics if a biofilm (bacterial layer) is present. In my terrariums, I see mold most often on driftwood branches, and that’s totally normal.
Is mold in a terrarium harmful?
Generally, no. While a small amount of mold may not be immediately harmful, it indicates an imbalance in the terrarium ecosystem. Mold can steal nutrients from plants, leading to their decline. 2. How do I get rid of white mold in my bioactive terrarium? A 1:1 solution of 3% hydrogen peroxide and water can be sprayed directly onto the mold.
How does Mold grow in a terrarium?
Mold requires moisture to grow, and the moist environment of a terrarium provides the perfect host. Mold spreads by releasing spores into the air, which then settle in suitable locations to grow and thrive. So, now you understand what mold is in general, right?
How do you remove moldy substrate from a terrarium?
To remove moldy substrate and provide a fresh environment for your terrarium plants: Completely remove the old substrate from the Terrarium. Select the new substrate that drains well and is suitable for the plant species. Add the new substrate to the Terrarium and replant the vegetation.