How to Fix Mold in Terrariums (7 Easy Tips & Tricks)

Terrarium mold, our fuzzy mortal enemy.

It’s always lurking, ready to strike. But is it actually a worry or just a nuisance?

Personally, I’ve encountered mold in a lot of my terrariums. It’s common to see a signature mold “bloom” as new terrariums settle in.

So, I’m either super unlucky, a terrible terrarium maker, or just maybe – it’s a pretty normal process.

In this article, we’re going to look at why mold is not something to panic about, and I’ll offer some techniques to address it should you need to.

mold in terrarium

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Is Mold Harmful to Terrariums?

Generally speaking, mold doesn’t affect healthy plants.

I mean, if it starts to take over the whole terrarium, then it becomes more of a problem. But a little bit of fuzz is not a serious threat.

Mold is a type of fungus, and fungi are saprotrophic. 

Meaning they are involved in the processing of decayed organic matter. Terrarium mushrooms actually fall into this category, too; they’d all generally feed on fallen leaves and perished plants in the wild.

So, as long as your plants are healthy, mold shouldn’t pose much risk to them.

mold on deceased part of fern frond
The mold is exclusively on the deceased part of this fern – not the healthy part.

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.

Mold on driftwood branch
Mold is a somewhat frequent reality in the terrarium hobby, but thankfully, it’s more of a nuisance than a problem.

It’s like a bad neighbor. It shows up to annoy you every time you make something nice, but if you give it some air and ignore it long enough, it’ll often go away on its own eventually.

Where Does Terrarium Mold Come From?

Mold is a natural phenomenon; it’s everywhere.

All it needs to flourish is a warm, moist environment with plenty of organic matter to feed on, in other words… a terrarium.

Sadly, mold is one of those things that’s hard to eliminate completely because it reproduces via microscopic spores.

Mold on terrarium moss
Spores can lay dormant for long periods and spread through the air to form new colonies.

They can enter your terrarium via the following:

  • Soil – Some soils come sterile packed (so they’re sure to be safe), but many soil mixes are likely to contain spores. Native soil taken from the wild will be riddled, so I’d stay clear.
  • Plants & mosses – Spores can hitch a ride on top of plants and amongst mosses. Sure, there are some interventions to deal with mold colonies on plants, but there’s not really an effective way to cleanse plants and mosses of spores.
  • Hardscape branches – There are a lot of sugars to be found in living woods, even if they’ve been treated or bleached over the years. They’re a perfect breeding ground for mold colonies.
mold on terrarium wood
It’s extremely common to see a bit of fuzz on spiderwood.
  • The air – If you have mold in your home (or wherever you build your terrariums), there’s a chance that there are enough spores in the air to germinate. We live in an old Edwardian flat; it’s beautiful but definitely not mold-free…

Most molds need a water content of over 70% to start germinating. So generally, it’s the surfaces where water beads or gets absorbed that are most at risk.

Moldy Terrarium? Here Are Your 8 Options

Treating a Little Bit of Mold

#1 Add some springtails – These beneficial terrarium insects are voracious mold eaters (and don’t eat your plants). So, introducing a colony at the first sign of fuzz will do wonders to keep your terrarium healthy and happy.

This really is the best option on the list, as it works as both a solution and a deterrent.

Springtail culture up close
One of my old springtail cultures ready to be added to a terrarium.

👉 You can grab terrarium springtails from our shop.

*It is worth noting that this is a better prevention than a cure; they’re only little critters, after all. So if there’s already a tonne of mold, they can struggle to get on top of it.

#2 Spray with chamomile tea – Chamomile tea is a mild organic fungicide thanks to its rich sulfur compounds. Personally, I didn’t find this was potent enough to actively combat the existing mold on my driftwood branches, but it did stop it from getting worse.

Mister with chamomile tea inside
A light spray with chamomile tea is always a good idea. It doesn’t harm the plants, smells wonderful, and has a protective effect. Just be careful not to add too much water to the system.

#3 Air it out – Mold thrives on moisture, so opening up any closed terrarium systems and increasing airflow will reduce both the humidity and total water level in the container.

This is the first thing I do at the sight of mold – I find most new blooms run their course in a couple of weeks, so sometimes it’s all you need to do.

mold on terrarium background
The mold on this terrarium background disappeared on its own with a little airing out.

Treating a Lot of Mold

#4 Remove and quarantine – If the mold outbreak is localized to certain plants or hardscape elements, you can remove the affected objects and quarantine them elsewhere.

#5 Dab with hydrogen peroxide – Thanks to its fizzing action, hydrogen peroxide is an effective way to kill mold on porous materials. The 3% solution is sold in supermarkets and recommended across the web. Simply dip a Q-tip in the solution and go to work.

wiping terrarium mold with q tip
That said, I’ve tried wiping mold away with Q-tips before, and it’s a real pain… You’ll need a lot of Q-tips and even more patience to get through a big outbreak this way.

#6 Swap out the substrate – If all else fails, and you think the substrate is likely to be the cause, re-potting the whole terrarium in a sterile medium is a good Hail Mary option. Though, for obvious reasons, it kind of means starting from scratch…

My Recommendations For Preventing Mold

We all know prevention is better than cure, so how can we stop it from happening in the first place? 

Well, I’m happy to say that a good setup goes a long way. 

#7 Use activated charcoal in your build – It’s a tale as old as time that charcoal prevents mold outbreaks by purifying the water, and while it’s really hard to say exactly to what extent, it certainly can’t hurt.

activated charcoal in hand
You can add a layer by itself above the drainage layer or mix some in with the substrate which has the added benefits of boosting aeration and drainage.

👉 See the activated charcoal for terrariums on our shop.

#8 Get technical – This isn’t appropriate for every build, but for larger tank-style pieces, you can incorporate fans and ventilation. It will promote natural air circulation that replicates a jungle environment, making sure mold isn’t able to take hold.

I’ve even seen people use computer fans for this.

But honestly, my number one tip still has to be to add a springtail culture to your terrarium (even new and healthy ones!).

It’s a cheap and effective way to never have to deal with mold. It’s a no-brainer.

In the project for my Essential Guide to Tropical Terrariums, I used springtails (along with solid building and watering practices recommended in the guide), and it hasn’t shown a hint of mold.

Got Terrarium Mold? Join the Conversation

Do you have an effective means of stopping mold in terrariums? I’d love to hear it.

I’m also interested in hearing any stories where mold has completely ruined a terrarium (for science of course!).

Good luck and stay safe out there!

51 thoughts on “How to Fix Mold in Terrariums (7 Easy Tips & Tricks)”

  1. I made my first paludarium which has flowing running water streams and one big pond at the bottom. It’s been a nightmare with white mold causing me health problems like heart palpitations and insomnia. Just going to get rid of it despite it’s beauty, 5 year old bonsai, and spending 300$ to make it.

    1. I’m so sorry to hear that Kyle! Your paludarium sounds stunning. I imagine trying to manage mould in a container with still water, running water and earth (at a variety of water saturations) must be a real challenge.

  2. Ive got a question if my driftwood got mold on it and i just removed it completely, removed my substrate and used paper towels for a little while, and disinfected my terrarium would that kill off the mold or keep the mold from developing? Is the driftwood the only problem? will it come back even if i put paper towel for little while and if i have no driftwood at all?

    1. Hi Issaq, to be honest I don’t think you can ever fully prevent mould from occurring in terrariums. The driftwood isn’t so much the cause, but more so the catalyst. Mould is much more likely to bloom on driftwood because the surface is full of exposed sugars and it tends to absorb a lot of moisture.

      So, to answer your questions;
      1. Removing and drying everything would probably kill off the initial mould bloom, but wouldn’t necessarily stop it coming back (it didn’t for me) as it’s near impossible to destroy all the spores.
      2. Driftwood is not the only source of the mould, but is likely to be a driving force behind it. Removing the driftwood altogether may help, but again, can’t guarantee it will stop it.

        1. Hi Dan, Ray and tribe.
          I work with my daughter at her floral store the Floral Emporium in the Yarra Valley.
          We created afew terrariums with good success but I wish I had come across your web site previously.
          Just find it a brilliant resource, thankyou.
          My question ….how do i use driftwood that is not sterile.
          Wild you could say.
          Second question.
          My wild stringtails in the garden are black. Are they the same species you use?
          Thanks for any reply.

          1. Hi Jillian, a lot of aquascapers boil their driftwood for an hour or two to sterilise it before use, but personally we just give ours a good rinse and use springtails in the build. Though it depends on what you mean by wild – I wouldn’t recommend adding a decomposing piece of wood from outdoors to your terrarium. As far as the springtail question, there are over 9000 species of Springtail so I highly doubt they’d be the same. Hope this helps! 😇

    2. I found lime sulphur solution painted on driftwood prevents rot and mould. I’ve used this technique on driftwood for bonsai. I guess it would work with terrarium hardscape too.

    1. That’s a good question! You could certainly argue that a layer like that would be separating the moisture in the soil from the air, so it might indeed reduce the ability for the mold to form. Worth a try 😊

  3. It looks like my succulents are not in any type of soil. It looks like black small stones. These stones are now turning green. I would assume this is a type of mold. Can you suggest how I would clean this up or have to change the medium.

    Thank you

    1. Hi Sandi, I don’t have much experience with succulents I’m afraid, but I know that mold can only thrive in damp environments. I’d imagine letting it dry out for a prolonged period (succulents should be able to handle this) would cause the mold to naturally die off.

    2. Hi Sandi, I am pretty well versed in succulents and here’s my suggestion: I would try wasing the green most likely algae growth from the gravel if you can. To do this I reccomend putting it in a wire mesh siv or a strainer of sorts and run hot water over it you can try and wash off by using a scrub brush, sponge, or even ribbing on a pair of cleaning brush. If you can’t get it off or would rather start over you can get some new gravel completely. You will want to mix or buy premixed some succulent and cacti substrate which is a mixture of sand, dirt, and some gravel or small rocks, and you can add in coconut fiber. Remember that there are so many kinds of succulents so you may want to take the time to get to know that species and it’s needs. I use the Planta app on my phone to find out what many plants are. I hope my advice helps you in some way!

    1. If it’s just a bit of white fuzz, usually just a couple of weeks. If it’s something much thicker and darker, you may need to take a direct approach, e.g. airing out the terrarium.

  4. I found some woody vines I want to use in my tree from terrarium and I was honestly thinking about putting a thin layer of silicone around them in case they mold out and don’t hold up to the moisture. Do you think that would prevent this from happening if I dry the vines out?

    1. Hey Joe, can’t say I’ve ever tried covering wood in a protective layer of silicone before! I’d imagine it would work to stop mould (as it would be sealed off from the air and moisture) but it sounds like a messy process!

  5. Hi Dan so I’ve just completed putting together my first terrarium for a crested gecko. I have springtails and Isopods in it already and am planning on getting the gecko soon but just found some pale green fuzz on the bottom of my cork bark backing and one branch of driftwood. It’s not bad and I’m hoping my bugs take care of it but what are some suggestions when adding in a reptile addition.

    1. I’m afraid I don’t have much experience with animals, just plants! I’d imagine the springtails and isopods will make short work of the mold, but I daren’t speculate on how it might affect a gecko.

  6. Yo, to all of you terrarium, vivarium, and palidariumists out there with mold taking your tanks over, ultraviolet and infrared light fixtures massively reduce and sporous fungi, whether pre or post germination. Technically speaking, these are usually marketed as aquatic algae combatants, but they don’t function exclusively as such. It’s the reason so many aquarium filters have UV/IR bulbs in them. This can apply, equally effectively in my experience, to terrariums, as light can travel through air as easily as water. Assuming the majority of you have planted tanks, you’d already have a light fixture, just look for a bulb at a PetSmart or whatever’s closest. I personally have multiple setups with humidity levels above 80%, some of them with a constant feed of fog/mist, and the four effective stops I use are isopods, charcoal in the misting systems, light fixtures, and most importantly, a well lit and ventilated tank. Hope this helps

    1. It will kill mold; however, UV is destructive to anything with DNA, which is why it it is such an effective disinfectant. Plants themselves have DNA, so I would use the light with care if plants are involved.

  7. a seed on the rock bottom has germinated and is starting to grow upwards. i just wanted to ask if its roots will rot and be a problem for the terrarium.

    1. Good question! Depends on the plant I’d imagine, some plants will happily grow in water whereas others will quickly rot. If you can get it out easily, I probably would, but I don’t think it poses too much of a risk to the whole terrarium.

  8. Hi Dan, thank you for the information/advice. Six months into creating terrariums (open and closed), and mini-scapes, I have mainly been battling those pesky fungus gnats. Winning, I think!
    Recently acquired and used some beautiful driftwood pieces, and now noticing some mould forming in one closed terrarium, on the driftwood. I am prepared to see where it takes the terrarium and me though, before trying to treat.
    It’s all a learning curve and I am enjoying the adventure thus far. Cheers.

    1. Hi Robyn, you’re so very welcome! Sounds like you’re really taking to the art of terrariums 🙂 Driftwood can be a little finicky with mould at first. Even after boiling and scrubbing the wood it came back for me, but then after a few weeks in the terrarium it went away and stayed away (for over a year now).

  9. Hi Dan. I created my 1st terrarium with 4 plants (2 ferns, 1 polka dot plant & another plant (I can’t recall the name but it looks like lemon coral sedum & is supposed to spread like ground cover with a beautiful green chartreuse color. I used LECA instead of gravel at the bottom, then a mesh piece, then horticultural charcoal and then the potting soil. I wasn’t sure how much potting soil to use but wanted to be sure the root balls were properly covered. The container is 10 1/2″ in height with an opening at 8″. So, there is 4″ of soil in the terrarium now. Is that too much soil? Also, to top dress the soil, I used a preserved sheet moss I bought at Hobby Lobby. I’m guessing preserved sheet moss after staying wet will likely produce mold inside a closed terrarium. So, after reading your site & info this morning, I removed all the sheet moss and have the lid off with the soil exposed to “air out”. Can I buy living moss to top dress the soil from my local florist? Is there any moss at craft stores that won’t cause mold to top dress with since moss gives it such a finished landscaped look? Since this was the first time I created a terrarium, it’s been a learning curve for me and, of course, I would like to avoid mold issues if at all possible.

    Thanks for any advice. If having to re-do my terrarium means better success for terrarium & plants overall, then I will gladly re-do my terrarium to improve it if something needs to be corrected. Thanks again,.

    Thank you.

    1. Hey Nancy 🙂 To answer your questions; 4′ of soil sounds fine, yes you can often buy living terrarium moss from florists (I like bun moss best), not sure about getting moss from craft stores. In theory, all moss is at risk of developing mold but it’s not something to worry about up front. It sounds like you’re on the right track!

  10. Hi Dan,

    This past weekend I finally put together three terriaums and used activated charcoal, potting soil, sheet moss, drift wood and pebbles. I have a rabbit fern in one of them and for the other two I have some nerve plants. In about three days I noticed white fuzzy mold growing on the sheet moss and now on parts of my nerve plants (leaves) ….first reaction was, “Ahhhhhhhh nooooo.” After reading your advice I feel much better haha and will let it run its course. I look forward to one day not seeing the white fuzzy mold because at first glance it’s concerning. I will try airing out my terriaums as well.

    Thank you again for your advice!

    1. Hey Ash, it sounds like you’re on the right track! Adding some springtails can help a lot too, but I’m sure with some extra airflow it’ll work itself out eventually 🙂

  11. Hi Dan,

    I am new to the terrarium world, wanted to ask is there any pre-work need to be done before put all the plant, wood, stone and etc into a terrarium.

    Recently I complete my first terrarium which have the following:
    1. Volcanic stone False bottom
    2. succulent substrate
    3. Few driftwood
    4. 4 Succulent
    5. Moss

    However, it start growing mold on the driftwoord after a few day. Having a big headache now.

    1. Hi! Some people like to boil driftwood before adding it, but to be honest I’ve tried that and it didn’t stop the mold. Personally, I think all driftwood is prone to mold at first, but mine went away on its own after a while.

  12. Hi Dan,

    Thank you fro your post, it makes me feel so much better that mould is a common cause. I mean everything driftwood I use tends to bloom with mould.
    I read in the past that Cynamon is helpful it worked on driftwood, I sprinkled on top and let it dry for a day or two and then out back on my scape.
    But I didn’t know about camomile tea, and I might invest in some isópode too.
    Thank you so much for your post, vey insightful .
    Ana

  13. Hello, I’m new to the terrarium craft. I have a white mould on the bottom rock layers of my closed terrariums. Layers are big rocks, activated charcoal, pebbles, sheet moss, and soil. The one that has the biggest problem has an orchid and orchid bark, not soil. I have opened all the terrariums to air out. What should I do about the mould in the bottom layer?

    1. Sounds like a tricky place to target! I’d honestly try to let it dry out as much as possible and start adding chamomile tea to your water.

    2. I’m having this same problem, but the mold has crept up into the substrate. It’s growing VERY quickly and will be at the surface soon, and I have a gecko in there. It’s really unpleasant because I think I’m going to have to ditch the whole substrate and start over, which means I have to emergency-build a whole new vivarium AND start over on the isopod population – and they were doing so well! The isopods were THRIVING, I’m really upset that I’m going to lose them. But I don’t know what else to do. Did you end up taking care of this?

  14. Hi Dan,
    I’m a complete novice and struggling with my terrarium I made about a month ago, mould appearing on one of my plants and it’s leaves. I’m worried it’s dying (looks to be drooping) but don’t know what to do. I’ve taken the lid off to air it out, is my best option to wait for it to dry out a bit? Do I remove leaves with mold on?

    1. Hi Charlie, there’s no easy answer I’m afraid. If it’s just a little mold then a bit of airflow and drying time might do the trick, but if it’s really taken hold then pruning/removal might be a better option.

  15. Hello Dan,
    Greetings from North Carolina! The one thing I aways do with my close terrarium when I can no longer see the plants inside because of the beads of water along the sides I found its a good practice to remove the lid for at least twenty- four hours and so far no problems with mold. I do plan on adding some moss along with a few more plants.

  16. I find it’s helpful to bake new or even old wood that’s going into a vivarium or terrarium just long enough that the wood is heated through to at least 250F. It will kill any mould spores and mites or other unwanted fauna that are on the wood though it can’t help with mould spores that find the wood later. Mind, the wood has to fit into the oven and sometimes a significant other may object to this. I haven’t got one of those so I can do as I like.

    In my big vivariums I sometimes spot treat a nasty bit of mould with a mixture of baking soda and water. 1-2 tsp baking soda per quart of water. I set the spray nozzle for a single tight stream that does not spread out and keep a towel immediately under the area to catch as much of the runoff as possible.

    Usually I’ll rinse the spot immediately afterward with distilled or RO water. I also use springtails and isopods but in new set ups that are not yet fully bioactive this can help ‘til the cleanup crew is established.

  17. Hello, Dan.
    Thank you for your wonderful site. It convinced me I could make an enclosed terrarium. I have some white fuzz on a piece of tree bark where I attached some British Soliders. They’ll be ok, right? I followed your special “potting soil” recipe. I remove the lid when I think it might be too moist and for air flow. About the creatures; won’t they crawl out? What is to keep them in? What happens when the terrarium becomes overrun?
    I have other questions, but I‘ll post those in the appropriate section.
    Thanks again for the fun and experiment!

    1. Hi Klaren, a springtail population will self-regulate so you don’t need to worry about it being overrun, if the lid is off for a while one or two might pop out but they really are tiny.

  18. I’m new to terrariums, so I appreciate the info! I just wanted to point out that the photo just under “Where does the mold come from” is actually the sclerotia of Leucocoprinus birnbaumii, a mushroom. It’s common in potted plants.

  19. I used to treat mold with cinnamon. it works in my closed terrarium but like you said the best way are using springtails.

  20. I picked up some petrified wood at the last rock show. It looks just like wood but none of the organics to carry mold spores.

  21. Maybe we need to start thinking of mold as part of the biologically active world we create when we make a terrarium. Of course, we don’t usually want to end up with a glass box filled with white fuzz! Ew! But a little mold along the way is just a form of decomposition, and decomposition features pretty prominently in a moist terrarium. We don’t need to cherish it, but neither do we need to overreact to its inevitable appearance.

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