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Opening A Closed Terrarium: When It Might Be Necessary

I recently made a closed terrarium from some native plants in my area. One of the questions that popped into my head while putting it together is can I and should I open up the terrarium once in a while?

Here’s the answer: a closed terrarium might need to be opened for several reasons, including re-watering, airing out the carbon dioxide, pruning, and removing dying or decaying plant parts. Generally, any sort of maintenance that needs to be done will require you to open up the terrarium for a few minutes to a couple hours once every few weeks.

So how can you tell when you would need to open up your terrarium? There’s a few signs you can watch out for to figure that out.

When you should re-water your closed terrarium

Probably the first reason that people will think about before deciding to open up their terrarium is to re-water their plants.

While a terrarium may be a closed ecosystem, the water levels need to be monitored on a regular basis to determine if it needs more or less water in the system.

One of the things you can check at a quick glance is the condensation levels on the container. 

Terrariums are generally supposed to have condensation on the glass in the mornings and evenings.

If you don’t see any condensation, that’s going to be a sign that needs to be re-watered. You can just open it up and give a quick misting to re-water it.

On a similar note, if you see condensation on the glass all the time, that’s a sign that there’s too much water in your terrarium. That could lead to root rot and promote the growth of mold.

In this case, you may want to open up your terrarium and wipe off the condensation on your container. You could also leave it open to allow some of the moisture to evaporate for a few hours.

A couple other ways you can check the water levels: if you see that the plants are droopy or if the soil feels dry to the touch, that’s a sign that more water needs to be added.

Generally speaking, a terrarium should only need to be re-watered once every few months. So don’t stress yourself everyday wondering if you need to open it up to re-water it. A quick check once every one or two weeks should be good enough.

How often you should air out your terrarium for fresh carbon dioxide

We all know that plants convert carbon dioxide to oxygen via photosynthesis. But one thing we need to be aware of is that if the plants are in a closed system, the carbon dioxide levels are slowly going to be depleted and converted to oxygen.

That’s why every once in a while it may be worthwhile to open it up to replenish the carbon dioxide levels.

In my opinion, this isn’t really something you will have to do consciously. If you’re already opening up your terrarium once in a while to do other sorts of maintenance, this problem should take care of itself.

But if it seems like you’re not opening up your terrarium very often, you might want to open it up once every one or two weeks for about 15 minutes to let in fresh carbon dioxide.

When to clean your terrarium container

Over time, you might start to notice that your terrarium container seems a little bit cloudy. This can reduce the amount of sunlight that will reach your plants.

It may be worthwhile to clean the container once in a while both to preserve the beauty of your terrarium and to allow light to get into your terrarium unfiltered. 

To do this, you will want to wipe off any dirt or algae that starts growing on your glass with a paper towel.

No need for any cleaning fluids as the chemicals could be harmful to your plants. Just watch the terrarium in the future to see if it needs more water if you removed some condensation from your cleaning session.

Sometimes you might see some mineral deposits that look like white residue on the glass over time. This can happen if you’re using tap water to water your plants. If you see any white residue that’s a little bit hard to wipe off, you can try using a 50/50 mix of water and white vinegar.

How to tell when to prune your plants

Many plants will grow if they’re pretty healthy. But in a terrarium environment, that might not be for the best.

It could lead to overcrowding and could detract from the original beauty of your terrarium when you first set it up. It could also be an issue if the leaves start touching the sides because that could lead to some rotting from the over exposure to condensation moisture.

If you see any yellowing or smell anything rotten in your terrarium, that could be a sign of plants being harmed by touching the walls.

Every once in a while, you might want to prune your plant a little bit. Give the leaves and/or the roots a little trim to cut them down a little bit and to slow their growth a bit.

Most plants can handle a little trim, just don’t cut the large tap roots, only the threads that grow from it.

How to identify and remove decaying plants

If you start to see any strange growths/colors on your plants that could be a sign of diseased, dying, or decaying plants.

One quick way to check for this is to open it up and just take a sniff. It should smell pretty fresh like a nice garden. But if you smell something rotten, that’s a telltale sign that something’s rotting or dying in there.

Don’t worry too much if you start to notice this. That’s a natural part of their life cycle and will happen to any terrarium no matter how well they are cared for. 

All you would have to do is to just remove any dying plants or any that look diseased. This might be necessary to prevent any disease from spreading to other plants.

Same thing goes for any moss or fungus growing in there. Just take out any plants with moss or fungus growing on them and rinse them out. You also want to look into reducing the moisture levels in there. Moss really loves to grow in overly moist environments.

You can use a small spoon or some chopsticks to remove the plant, but be careful to not disturb the roots of other plants. If you can, you can replace the plant with one of similar size and moisture requirements. 

When you do replace any plants in there, all you would have to do is dig a little hole and place the roots in there. Once planted, make sure that the roots are surrounded with soil without any air pockets.

Generally, you might need to replace some plants once or twice a year. But that depends on the type of plants you have in there and how well they were taken care of.

If things are starting to look really bad and you see more than 60 or 70% of your plants are dying or decaying, it might just be best to start over with a fresh terrarium. 

All in all, every closed terrarium will have to be opened eventually for routine maintenance. For the most part, it will just be to adjust the water levels, prune your plants, or some simple cleaning. Eventually, you may have to remove or replace some plants that are dying. But overall, opening a closed terrarium is nothing to worry about and is even encouraged for regular checkups on your terrarium’s health.