I get it, condensation in your terrariums can be super annoying.
Nobody likes a Gorillas in the Mist kind of situation with our plants playing the elusive protagonists behind a shrouded glass terrarium.

Fogging glass is a natural side effect of plant transpiration (we do want our plants to breathe after all) but too much condensation could be a warning sign.
Read on to find out how much condensation a healthy terrarium should have, and the steps we can take to reduce it.
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Why Does Terrarium Glass Mist Up?
First things first, if weāre going to try to tackle condensation forming on the glass, we need to figure out why itās doing it in the first place.
Generally, condensation happens because of two fundamental reasons:
- High humidity – Terrariums trap humidity within the glass containers (up to 100% relative humidity if its completely sealed) so thereās a lot more moisture in that air.
- Higher temperature – Most importantly, higher than the outside. Terrariums act like greenhouses, absorbing light and retaining heat. Water is condensing due to the difference in temperature between the inside and outside of your terrarium. If your cold-ass house is cooling the temperature of the glass, When warm terrarium air hits the cold surface, it reaches its dew point and condenses.
There are other contributing factors, but ultimately they all boil down to these two things.
Should a Healthy Terrarium Mist Up?
Arguably, yes. Itās a natural cycle.
The rate of transpiration (the evaporation of water from plants) depends on lots of factors, but most importantly for us itās down to light, temperature and humidity.
All three of those things are going to be heavily affected by the strength of the sun during the daty.
So thereās no surprise that plants will be transpiring most during the peak of the day, when the sun is at its brightest and warmest. So you can absolutely expect your terrarium to mist up a little during the morning, afternoon and definitely midday sun. At 30°C, a leaf may transpire three times as fast as it does at 20°C.
At night, when the external stimuli drop in intensity, plants dramatically reduce transpiration and so condensation will drop.
In many ways, itās important that water condenses and drops back down. It perpetuates the water cycle and makes sure our plants are getting constant nourishment.
But thatās not to say we need the water constantly sitting on the sides of the glass. In fact, a terrarium thatās constantly foggy likely has too much water in the system.
If your terrarium has excessive condensation 24/7 then youāre likely overwatering it!
How to Reduce Terrarium Condensation
Natural Solutions
- Keep your room temperature stable – Remember, water condenses on the inside of a terrarium because the terrarium air is warmer than the glass. If you can keep your house ā and therefore terrarium glass ā a stable warm temperature, it could drastically reduce the condensation level. If you can keep your terrarium glass warmer than the terrarium airās dew point, theoretically you could stop water condensing altogether.
- Use a magnet cleaner – Magnet cleaners (like this one) are usually reserved for cleaning algae from aquarium glass, but they can work in a terrarium too if your terrarium glass is large and flat. Itāll remove the condensation from the sides without removing it from the system like a cloth would. A quick fix rather than a permanent solution, but it does the trick!
- Open up your terrarium – Ventilating your terrarium occasionally will balance out the humidity a little. Just donāt leave it off too much, your tropical plants and mosses like that humidity after all.
Finally, if thereās too much condensation (i.e. even during the night) then you can also try this.
- Wipe the inside of the glass – I know, it seems almost insultingly obvious, but doing so not only immediately removes the condensation, but also removes water permanently from the system.
Artificial Solutions
* A quick note to say that these are experimental suggestions. I havenāt personally tried any of these, but Iāve seen them suggested or used somewhere in the world and they seem to have some merit.
- Install a fan – This is guaranteed to reduce, or even entirely stop condensation forming on the glass by improving air circulation. Itās a staple in most vivarium builds, but not so common in terrariums. Itās not ideal – because fans are unnatural and unsightly – but you can get some very small fans these days. This one is only 40mm wide so you can probably hide it if the terrarium is big enough and youāre creative with your setup.
- Create a ventilation valve – It kind of defeats the point of having a closed terrarium, but a small valve for ventilation might be enough to reduce condensation whilst preserving the majority of the humidity. These terrarium eggs from Design House Stockholm claim to have a spout that āalso functions as a valve that lets in air and regulates the moisture and temperature levels inside the greenhouseā. But I canāt personally attest to those claims.
- Spray the glass with water repellent – Some products such as Rain-X are used on windscreens a lot. They force water to bead up and drop off, so spraying a coating on the inside of your terrarium is sure to reduce condensation. If you do choose this route, Iād leave plenty of time between coating the glass and adding the plants. Though, even then, I canāt guarantee it wonāt harm your plants. Might be worth experimenting with, but maybe not on your favourite/expensive plants.
Over to You
Have you tried any of these solutions with success?
Iāve yet to experiment with any artificial solutions, but if they solve the problem with no damage to your plants, Iād love to hear your success story!
2 thoughts on “Can You Reduce (or Prevent) Terrarium Condensation?”
I found the best and simplest way to get rid of access moisture is to take the lid off for 5-10 minutes at a time,then monitor the cycle for a few days to see if corrected.If you over do it ,add only some water in a mist form from a spray bottle.
Great tip š