Common Terrarium Problems

Like any craft we work towards mastering, terrariums come with a learning curve and their own set of issues we will inevitably come across. These terrarium problems must be addressed to ensure the health and well-being of your beloved ecosystems.

In this article, we’ll discuss some of the most common problems found with terrariums and how to address them. Read on to learn more and keep your vivarium as healthy as possible!

Common Problems, Prevention & Treatment

When it comes to making and maintaining terrariums, these are some of the most common issues you will more than likely run into at some point. It can be frustrating to deal with these types of things but I hope this guide not only helps you navigate through the troubles…

But also shine a light on the fact that we all experience similar issues.

Poor Air Circulation

One of the most common problems found in terrariums is poor air circulation. This issue can arise from keeping your terrarium too small, overcrowding elements in a large container, or having a lid too tightly fitted to the container with no ventilation.

Without proper air circulation, the temperatures can become too high with stagnant air, leading to unhealthy or fungal conditions. 


Poor air circulation in a terrarium can lead to an accumulation of stagnant air, leading to increased humidity levels which in turn can create ideal conditions for mold, fungi, and bacteria to grow.

To reduce the risk of poor air circulation, make sure that all vents, air holes, and windows in the terrarium are open, clean, and not blocked in any way. If the setup doesn’t have ventilation, this will be a good indication one needs to be added.


To prevent this, it’s important to use a container with a lid that can be opened and closed to optimize airflow. Additionally, adjusting the size of your terrarium to the type of inhabitant is key to avoid overcrowding, as is frequently opening and closing the lid for air to flow.

Mold, Fungus & Bacteria Infections

Mold, fungus, and bacterial infections are some of the most common problems found in terrariums and can have serious consequences if left unchecked. Fungi grow best in damp, warm environments and are easily identifiable by their fuzzy or slimy appearance.

Bacteria are commonly caused by un-cleaned terrariums and are typically identified by an unpleasant rotting smell. 


There are many ways to address these types of infections. The first step will be to remove what you can with tweezers. What’s left can easily be killed off with hydrogen peroxide in a spray bottle or cotton swab. Lastly, springtails and isopods do an amazing job with eating mold and fungus so grab a colony and turn them loose.


To prevent mold, fungus, and bacterial infections from occurring, it’s important to keep your terrarium free from stagnant water, and always ensure the ventilation holes are open and free from obstruction.

Additionally, make sure to regularly clean and disinfect the surfaces of your terrarium, as well as any objects you introduce inside, such as toys and decorations. 

Algal Blooms

Algal blooms are a type of rapid growth of algae that can often be found in terrariums. Algae appear as green patches or streaks on the sides or ceiling of the terrarium, and can quickly spread if not treated.

Algal blooms are most commonly caused by too much sunlight and warm temperatures, combined with an abundance of nitrogen and phosphate from decaying organic material in the terrarium.


To treat algal blooms, it’s important to remove the affected areas as soon as possible. Use a razor blade to scrape off the algae and disinfect the surfaces with a diluted bleach solution.

In addition, reduce the amount of light entering the terrarium, and make sure to remove any decaying organic material regularly. Lastly, add several tropical or aquatic plants to consume the nitrogen and phosphate that are causing the algae growth. 


To prevent algal blooms, it’s important to make sure the terrarium is receiving enough light, but not too much. Furthermore, it’s important to avoid overcrowding the terrarium with too many plants or objects, as this can block light or prevent air circulation.

Lastly, make sure to regularly clean and remove decaying organic material. By following these steps, you can help reduce the risk of any algal blooms happening in your terrariums.


Overheating is a common problem in terrariums and can be caused by poor ventilation, overcrowding, incorrect lighting, or lack of appropriate water and respite areas, as well as improper substrate.

High temperatures can lead to a decrease in oxygen levels and an increase in humidity and therefore create ideal conditions for mold and other illnesses to spread. 


To reduce the risk of overheating, make sure to keep the terrarium in an area away from direct sunlight and other heat sources, and to open air vents or unmount the lid and keep them clear from any obstructions.

Pruning any overgrown plants, increasing circulation with a fan, and providing respite areas with shaded foliage can also help lower temperatures.


To prevent overheating, it’s important to ensure proper ventilation and not overcrowd the terrarium with too many plants. Additionally, make sure that the terrarium isn’t exposed to any direct sunlight or other heat sources, and create areas of respite with shaded foliage or leaf litter.

Finally, pay attention to the substrate used and check it periodically to make sure it is not retaining too much heat. By following these simple steps, you can help reduce the risk of overheating in your terrariums.

Too Much Humidity

Too much humidity in your terrarium can create ideal conditions for mold, fungi, and bacterial infections to grow, and can be identified by condensation on the walls and cloudy glass on the terrarium. 


To reduce the humidity levels, you can introduce more air circulation by opening lids and vents in the terrarium and adding a small electric fan to circulate air. As a bonus, you can place a dehumidifier in the area and check to make sure the water dish hasn’t overflowed.


To prevent a build-up of humidity in your terrarium, you can use water sparingly, make sure all ventilation holes are open and unobstructed, and set up a fan to circulate air. Try to avoid overcrowding your terrarium with too many plants and choose greenery that tolerates drier conditions.

Additionally, you can opt for terrariums with a self-contained water feature to reduce the amount of water used.

Poor Drainage 

Poor drainage is another common problem found in terrariums and is usually caused by soil that is too wet or too dry. This can lead to waterlogging, which can cause roots to rot and the growth of mold or fungus. Poor drainage can also cause a nutrient deficiency in plants due to a lack of oxygen in the soil. 


The best way to treat poor drainage is to replace the soil with a mixture of sand, vermiculite, and perlite, as these materials aid in aeration and moisture retention. If you cannot replace the soil, you can use a soil amendment such as sand and perlite to help improve aeration and drainage. 


To prevent poor drainage, always use well-draining soil and avoid overwatering, as this can cause the soil to become compacted and cause drainage problems.

Excess Water in the Soil

Excess water in the soil of a terrarium can be a common problem that can lead to numerous issues. When an excess of water accumulates in the soil of the terrarium, it can prevent air from getting to the roots of the plants, leading to wilting, root rot, and other issues.

It can create ideal conditions for algae and bacteria to form, further leading to more issues.


To treat a terrarium with excess water in the soil, you must identify the source of the water and take steps to reduce the rate of water accumulation. This might include checking all drainage holes, pipes, and other water sources and adjusting or blocking them as needed.

Additionally, if possible, all the soil and any plants with excessive water should be removed and replaced with dry soil.


When it comes to prevention, it’s important to make sure all drainage holes, pipes, and other water sources are working correctly and do not overflow. All plants with high water demands should be placed in low or moderate-light areas, and soil with particular absorbent qualities should be used to reduce water accumulation.

By following these simple steps, you can help reduce the risk of having excessive water in the soil of your terrarium.

Mites & Other Pest

Pests are one of the most common issues found in terrariums and can cause serious damage if left untreated. Mites, including red mites and spider mites, are tiny arachnids that feed on both plants and inhabitants and are small enough that they can crawl through the finest of spaces.


To treat mites and other pests, clean the surfaces of your terrarium with a nitrogen peroxide solution, and remove any affected plants or toys. Additionally, use a pesticide or miticide appropriate for the kind of mites and other pests you have in your terrariums. 


To prevent mites and other pests from occurring, monitor the air quality of your terrariums, and make sure to remove any decaying plant material, which can attract pests. Additionally, use a course wrap or sponge material to cover the ventilation holes to avoid any pests crawling through them. 

Poor Lighting 

Poor lighting is another common problem found with terrariums. This occurs when the terrarium does not receive an adequate amount of natural light or supplemental lighting, particularly in the winter months when the days are shorter and the sun is lower in the sky.

Poor lighting can lead to stunted plants, or they may even turn yellow and eventually die.


To fix poor lighting, it’s important to add proper vivarium lighting if natural sunlight isn’t available or adequate. You can also move the terrarium to a window that receives direct sunlight or use artificial lighting with a timer set to create a few hours of light each day.


To prevent poor lighting, try to position the terrarium in an area where it will receive maximum natural sunlight or provide supplemental lighting if needed. Additionally, use a timer or light sensor so that the terrarium receives the correct amount of light each day, even when natural sunlight is lacking.


By now, we hope you feel more equipped to successfully manage any problems that may arise with your terrarium. With these tips in mind, you’ll have no trouble maintaining a balanced and healthy ecosystem. Happy building!

Frequently Asked Questions

Terrariums generally need to be watered once every 12 weeks. Be sure to check the soil and plants regularly to ensure that the soil is not overly dry or wet.

The smell of a terrarium depends on its environment and the species of plants within it. In general, terrariums can have a slightly damp or musty smell due to water evaporating, and some plants can produce an odor. Making sure the terrarium is properly ventilated and adding an air freshener if necessary can help minimize any odors.

Unsuitable environmental conditions can make it difficult for a terrarium to thrive. Without the right light, temperature, humidity, and water levels, terrariums can fail. Paying attention to these factors and providing the appropriate care for your terrarium is important for keeping it healthy.

No, a fan is not necessary for a terrarium. Terrariums need to be properly ventilated, but generally, a fan is not necessary.

You should not put toxic plants, rocks, animals, or waterlogged soil in a terrarium.

It is likely due to high humidity levels combined with inadequate ventilation in your vivarium. To get rid of the mold, clean your terrarium with a solution of vinegar and water or hydrogen peroxide, reduce your vivarium‘s humidity level to below 70 %, and ensure that your vivarium has adequate air circulation.

To prevent root rot in a vivarium, be sure to use a soil mix that drains well and does not retain excess water. Keep the soil lightly moist and water with a spray bottle or dripping system on a regular basis. Monitor the temperature and humidity of the soil and be sure it is not too damp. Prune away any dead or decaying roots or plants to reduce the risk of root rot.

Many animals that are staples in bioactive terrariums (such as bearded dragons, leopard geckos, or dart frogs) can feed on mold, as can most insectivorous species. In addition, some species of isopods and springtails can consume mold and help keep it under control.

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