🌡 Terrarium Placement & Temperature: More Than Just Sunlight

When a terrarium begins to struggle, many people assume it must be due to direct sunlight. While sunlight can certainly cause overheating, it is not the only factor. In many cases, it isn’t the main one.

Even if your terrarium is placed out of direct sun, it can still overheat depending on where it’s positioned within your home. Terrariums are designed to be low maintenance, but they rely heavily on the ambient temperature of the room they’re kept in. If a room regularly becomes warm during the day, the terrarium’s internal environment will heat up as well.

🔥 Hidden Heat Sources to Watch Out For

There are several common placement issues that can cause unexpected and dangerous temperature spikes:

• Nearby heat sources
  Terrariums placed near heaters, vents, lamps, or other appliances can overheat quickly, even if those heat sources aren’t on all the time.
• Rooms that trap heat
  Spaces such as sunrooms, bathrooms, kitchens, and laundries often become significantly warmer than the rest of the house. Ovens, stovetops, dryers, hot showers, and limited airflow can all raise room temperatures to unsafe levels for sealed terrariums.
• Heatwaves and hot days
  During warmer weather, if the room itself becomes hot and there is no cooling (such as air-conditioning or adequate airflow), the terrarium will mirror that temperature and may overheat.

A good rule of thumb:
👉 If you walk into a room and it feels noticeably warmer than the rest of your home, it’s likely too warm for a sealed terrarium.

☀️ Direct Sunlight & the Greenhouse Effect

Placing a terrarium in a window or in direct sunlight creates a greenhouse effect. Heat builds rapidly inside the glass, and temperatures can rise to lethal levels very quickly, even if the terrarium has good ventilation.

For this reason, terrariums should always be placed in bright, indirect light, never in direct sun.

💧 Condensation: What Your Terrarium Is Telling You

Condensation is one of the best indicators of whether your terrarium is happy or stressed.

• A healthy terrarium shows a natural condensation cycle: light misting on the glass that clears and returns throughout the day.
• Constant heavy condensation (large water droplets that never clear) is a sign that the terrarium is too warm, too wet, or both.
• No condensation at all may indicate that the enclosure is too dry.

If your terrarium is continuously covered in condensation, simply moving it may not fix the problem. The built-up heat needs to be released.

What to do:

• Remove the lid for a few hours to allow excess heat and moisture to escape
• Wipe the inside of the glass to remove excess water if needed
• Once condensation reduces to a fine mist, replace the lid

⚠️ Avoid leaving the lid off for too long, as this can dry out the substrate and disrupt the terrarium’s balance.

🌱 Why Room Temperature Matters So Much

A terrarium’s internal environment closely reflects the ambient temperature of the room it’s placed in. This affects:

• Plant health
  Most terrarium plants thrive in a stable temperature range of approximately 18–24°C (65–75°F).
  • Too hot → plant scorch, excess condensation, stress, or collapse
  • Too cold → slowed growth and poor plant health
• Clean-up crew (springtails & isopods)
  These beneficial organisms also rely on stable conditions and may struggle if it’s too hot or too cold.
• Humidity & mould balance
  Heat increases humidity, which can lead to mould or bacterial growth if ventilation and temperature aren’t balanced.

🌿 Final Thoughts: Low Maintenance Still Needs the Right Conditions

Terrariums are designed to thrive with minimal care, but only when the conditions are right.

Placing a terrarium on a shelf and forgetting about it doesn’t automatically mean it will succeed. Thoughtful placement, stable temperatures, and occasional observation are key to long-term success.

If your terrarium is struggling, it doesn’t mean it was built incorrectly or that you’ve done something wrong. Often, a small adjustment like choosing a cooler room or improving airflow can make all the difference.

Your terrarium isn’t failing — it’s communicating. 🌱