Troubleshooting Common Terrarium Problems and Fixes

Common Terrarium Problems

Terrariums are miniature indoor gardens enclosed in glass containers. They allow you to create a small slice of nature right in your own home. However, as with any living system, problems can arise that need troubleshooting to get your terrarium thriving again. In this comprehensive guide, we will explore the most common terrarium issues you may encounter and provide fixes to get your terrarium back to health.

What are the Most Common Problems with Terrariums?

Some of the most frequent problems terrarium owners face include:

  • Excessive moisture and mold growth
  • Lack of drainage leading to root rot
  • Poor light exposure
  • Pest infestations
  • Lack of ventilation
  • Overheating
  • Plant decline and death

While terrariums are designed to be self-sustaining mini-ecosystems, they do require occasional maintenance and troubleshooting to ensure your plants stay happy and healthy. Catching problems early and making the right adjustments can make a big difference. Below we delve into the causes behind common terrarium problems and the solutions to correct them.

How to Fix Excessive Moisture and Mold in a Terrarium

Excess moisture is one of the most common terrarium problems. The enclosed environment means water can easily get trapped inside, creating 100% humidity. This allows mold and fungal growth to proliferate, which can be harmful to your plants.

There are a few ways to fix excessive moisture in a terrarium:

  • Improve drainage: Make sure your terrarium has activated charcoal or pebbles/gravel at the bottom above the soil layer. This creates a drainage system allowing excess water to trickle out of the soil.
  • Open the lid periodically: Leaving the lid open for a bit each day allows moisture to escape and reduces humidity. Start with a few minutes a day and increase as needed.
  • Add more ventilation: Drill a few holes (1/4″ diameter) into the sides near the top of the container. More airflow circulation prevents moisture buildup.
  • Use fewer moss layers: Reduce moss padding which holds onto moisture. Use it sparingly in select areas only.
  • Get a hygrometer: Monitor humidity levels. Ideal range is 50-70%. Adjust ventilation and lid openings accordingly.
  • Remove moldy plants/soil: If mold growth has already occurred, remove affected plants and top layer of soil. Replace with fresh soil to start again.

Controlling excess moisture through improved drainage, ventilation, and monitoring prevents recurrent mold issues. Act quickly at the first sign of high humidity or mold to avoid losing plants.

What Causes Poor Drainage and Root Rot in Terrariums?

Insufficient drainage is another common problem in terrariums. Without proper drainage, waterlogged soil becomes compacted. This prevents oxygen from reaching plant roots and causes them to rot. Signs of root rot include yellow, wilted leaves and stunted growth.[1]

Several factors can impede drainage in a terrarium:

  • No drainage layer: Lack of gravel, activated charcoal, pebbles at the base means water gets trapped in the soil.
  • Thick soil: Using regular potting soil or garden soil makes the mix too dense. This inhibits drainage.
  • Too many decorative layers: Excess layers of moss prevent proper drainage.
  • Compacted soil: Lack of aeration causes soil to become compressed over time blocking drainage.
  • Small container: Narrow terrariums constrain soil and roots limiting drainage.

To improve drainage and prevent root rot:

  • Add activated charcoal, gravel or pebbles below the soil
  • Use a well-aerated soil mix specifically for terrariums
  • Limit moss layers
  • Regularly mix up and aerate soil to prevent compaction
  • Choose terrariums with adequate width for healthy roots
  • Ensure container has drainage holes so excess water can escape

With proper soil layers and mix, your terrarium will have the drainage it needs to allow oxygen to reach plant roots and prevent decline.

How Often to Water Plants in an Open vs Closed Terrarium

How Much Light Should Terrariums Get?

Insufficient lighting is a common reason many terrarium plants fail to thrive. Light fuels photosynthesis allowing plants to grow and produce energy. The glass walls of a terrarium cut down on light penetration. And indoor lighting may not provide the full spectrum of light plants need.

Here are terrarium lighting guidelines for optimal plant growth:

  • Indirect or filtered sunlight: Direct hot sun will overheat a closed terrarium. But placing near a brightly lit window provides brighter light.
  • Artificial full spectrum lighting: Use grow lights or full spectrum bulbs that provide light wavelengths for photosynthesis.
  • 12-14 hours daily: Ensure lights are timed to provide consistent daylight hours.
  • 3000-5000 Kelvin bulbs: Kelvin rating indicates color temperature. 3000-5000K mimics natural daylight spectrums.
  • 6500-8500 lux intensity: Measure light intensity with a lux meter. Aim for readings in this range at plant level.
  • Light positioning: Place lights very near the top or sides of the terrarium so plants in the center get sufficient exposure.

With planning, you can provide the quality and intensity of light your terrarium plants need to thrive through natural sunlight or artificial lighting systems.

How to Deal with Pests in a Terrarium

Annoying gnats, fungus flies, mites, and other pests are drawn to the warm, humid environment inside terrariums. They can rapidly multiply and damage plants.

Here are tips to tackle common terrarium pests:

  • Let soil dry out: Fungus gnats/flies thrive in constantly wet soils. Allow the soil to dry out slightly between waterings.
  • Remove decaying matter: Eliminate rotting leaves, dead plants, and detritus where pests can breed.
  • Clean with soap solution: Wipe down glass walls and decor items with a mild soap solution to remove eggs.
  • Introduce predatory mites: Beneficial mites feed on pest mites. They naturally control populations.
  • Sticky traps: Use yellow sticky cards or tape near vents to catch adult flies and gnats.
  • Fly paper: Unscented fly paper hung inside can help reduce adult fly populations.
  • Diatomaceous earth: Sprinkle this powdery abrasive on the soil. It damages exoskeletons of crawling pests.
  • Cloves or cinnamon: Sprinkling these aromatics repel fungus gnats. But avoid getting on plant leaves.

With vigilance and prompt actions like cleaning, drying out the soil, and using natural remedies you can get a terrarium pest infestation under control. Introducing predators like beneficial mites creates lasting pest management.

How Much Ventilation Does a Terrarium Need?

While terrariums are designed to be self-contained systems, they still require some ventilation. Ventilation allows for airflow which provides fresh oxygen, releases excess humidity, and controls heat.

Here are some tips for providing proper ventilation:

  • Keep the lid slightly ajar or open it briefly each day. This prevents stagnant stale air and allows airflow.
  • Drill small holes (1/4” diameter) near the top edges of the glass walls. Add 2-4 holes on each side for cross ventilation.
  • Use screen panels instead of glass for parts of the walls or lid. Screen allows more airflow while still containing the environment.
  • Add a small computer case fan. Hide it behind plants. Use a low speed setting to gently circulate air.
  • Place the terrarium on risers or feet. This allows better airflow under the bottom of the container.
  • Use an aquarium air pump outside the terrarium to push air in through tubing.

Monitor humidity levels with a hygrometer. Ideal humidity is 50-70% which is achieved through moderate ventilation. Adjust ventilation upwards if humidity rises too high. With the right balance, ventilation provides fresh air exchange while still keeping stable humidity.

Why Do Terrariums Overheat and How Can It Be Prevented?

The closed environment of a terrarium makes it prone to overheating. Excess heat causes plants to wilt, dry out and decline.

Several factors can contribute to a terrarium overheating:

  • Excess sunlight: Direct hot sunlight hitting the terrarium raises temperatures to unacceptable levels.
  • Lack of ventilation: Stagnant air gets increasingly hot without vents or gaps for airflow.
  • Incandescent bulbs: These release more heat. Use cooler LED or fluorescent lighting.
  • Large container: More volume of air holds more heat. Choose a modest sized container.
  • Too many plants: Excess plants packed together prevent cooling airflow.

To prevent overheating:

  • Site the terrarium away from direct sunlight. Use sheer curtains to filter light.
  • Open the lid or add ventilation holes to allow hot air to escape.
  • Use a thermometer inside to monitor temperatures. Ideal range is 60-80°F.
  • Mist plants daily to increase humidity. As water evaporates from leaves it provides a cooling effect.
  • Choose low wattage LED or fluorescent lights which stay cool. Position off to the sides rather than overhead.

With a little trial and adjustment, you can maintain ideal temperatures to prevent heat damage to your terrarium plants.

What Causes Plants to Deteriorate and Die in Terrariums?

If plants begin to decline, turn yellow, wilt, or die, something in the terrarium environment is amiss. The most common problems that lead to plant deterioration are:

  • Insufficient lighting: Without adequate light for photosynthesis, plants slowly starve and decline.
  • Overwatering: Too much moisture leaves roots waterlogged and susceptible to rot.
  • Underwatering: Allowing plants to dry out too frequently desiccates leaves and causes wilt.
  • Poor drainage: Roots suffocate without proper aeration and oxygen circulation.
  • Extreme temperatures: Too hot or too cold stresses plants.
  • High humidity: Excessive moisture encourages fungal diseases.
  • Pests: Insect infestations, mites, and fungi damage plant tissues.
  • Improper soil: Heavy, dense soil or lack of nutrients causes poor growth.

To get a declining terrarium thriving again:

  • Evaluate lighting, temperature, humidity and make needed adjustments.
  • Check soil moisture and water plants when just slightly dry.
  • Ensure drainage layer is present and soil mix is light.
  • Remove dead plants/leaves which can breed pests and diseases.
  • Treat any obvious pest issues.
  • Fertilize with a weak solution to provide missing nutrients.
  • Trim off dying parts to stimulate new growth.

With a few troubleshooting tweaks to get conditions right, deteriorating plants can rebound again!


Terrariums allow you to create a lush miniature world, but they do require some simple maintenance and troubleshooting to keep plants healthy. Monitoring conditions and making adjustments to lighting, humidity, ventilation, drainage, and pest control prevents major problems and plant decline. With the right balance, your terrarium can thrive for many years, providing a beautiful, fascinating ecosystem to brighten your indoor space!

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *