Terrarium pests explained: From springtails to Fungus Gnats
Spotting tiny insects inside your terrarium can be alarming. You carefully built a balanced miniature ecosystem, and now small creatures are crawling through the soil or along the glass. The good news is that insects in a terrarium are common and in many cases, they are harmless or even beneficial. Because a terrarium is a living ecosystem with soil, moisture and organic material, it naturally attracts microorganisms and sometimes small insects. The key is understanding which insects are normal, which can become problematic and how to restore balance if needed.
Why do insects appear in a terrarium?
Insects usually enter a terrarium through soil, plants, or tiny eggs that were already present when you built it. Since terrariums provide warmth, moisture and organic matter, they create an ideal environment for certain species to thrive. Excess moisture, decaying plant material and poor airflow increase the likelihood of insect activity. A newly built terrarium may show some life in the first weeks as the ecosystem stabilizes. In most cases, this settles naturally over time.
Common insects in terrariums
Springtails
Springtails are tiny white insects that live in the soil. They are actually beneficial. They feed on mold and decaying organic matter and help keep the ecosystem clean. If you see very small white specks jumping in the soil, they are likely springtails. There is no need to remove them.
Fungus Gnats
Fungus gnats are small flying insects that resemble fruit flies. Their larvae live in moist soil and feed on organic material. While a small number is not harmful, a large infestation can damage delicate roots. Fungus gnats usually appear when the soil stays too wet for too long.
Soil Mites
Tiny white or translucent mites may occasionally appear. Most soil mites feed on decomposing material and are harmless, though large populations can indicate excess moisture.
Isopods
In some bioactive terrariums, isopods (woodlice) are intentionally added. They help break down organic matter and contribute to a healthy system.
Insects in a closed terrarium
Closed terrariums maintain high humidity and recycle moisture. If insects appear here, it often means the environment is too wet or contains too much decaying plant material. If you notice fungus gnats flying inside the glass, reduce moisture immediately. Open the lid and allow the terrarium to air out for several hours. Remove fallen leaves and trim dying plant parts. In persistent cases, replacing the top layer of soil may help.
Springtails, however, are generally a positive sign in a closed ecosystem, as they help control mold naturally.
Insects in an open terrarium
Open terrariums behave more like traditional plant pots. Fungus Gnats are more common here, especially if succulents or tropical plants are overwatered. Allow the soil to dry completely before watering again. Improving drainage layers with hydro stones and activated charcoal helps prevent stagnant moisture. Sticky traps placed near (not inside) the terrarium can reduce adult gnat populations without disturbing the ecosystem.
Are insects dangerous for your terrarium?
In small numbers, most insects are harmless. Some even contribute to a healthy micro-ecosystem. Problems arise when populations grow too large, usually due to overwatering or excess organic waste. The presence of insects is often a symptom of imbalance rather than the core issue. Correcting moisture levels and maintaining cleanliness typically resolves the problem.
How to prevent insects in a terrarium
Prevention starts during setup. A base of hydropallets prevents water from collecting around the roots, while activated carbon helps filter impurities. Water moderately, especially in closed systems. Remove dead leaves quickly and prune plants before they overcrowd the container. Good light placement also supports strong plant growth, making them more resistant to pests. If you’re building a new ecosystem, our terrarium starter and refill kits include carefully selected layers to promote long-term balance.
