If you’ve noticed black tiny flies in your terrarium, you’re likely dealing with fungus gnats. These small pests thrive in humid, enclosed environments and lay their eggs in damp soil. While they don’t harm humans, their larvae can damage plant roots and disrupt the balance of your terrarium.
The good news? You can eliminate fungus gnats naturally without harming your terrarium’s delicate ecosystem. Here’s how to spot, remove, and prevent fungus gnats effectively.
How to Spot and Recognise Fungus Gnats in a Terrarium
Fungus gnats are often confused with fruit flies, but they have some distinct characteristics:
🔍 Small black flies hovering above the substrate – They are weak fliers and tend to crawl on surfaces rather than flying around.
🔍 Larvae in the soil – Small, translucent worms with black heads may appear if you disturb the top layer of the substrate.
🔍 Unhealthy plants – In severe infestations, plant roots can become damaged, leading to yellowing or wilting leaves.
🔍 Excess moisture – If the soil stays too damp, it becomes a breeding ground for fungus gnats.
How to Get Rid of Fungus Gnats in a Terrarium
If you spot black tiny flies in your terrarium, take action before they multiply. Here’s how to remove them effectively:
1. Open the Terrarium and Remove Adults Manually
Fungus gnats are weak fliers, making them easy to remove by hand.
✔ Open the terrarium to improve airflow.
✔ Use a small stick or tool to gently guide the gnats out.
✔ Be patient—this method requires repeated efforts over several days.
2. Use Double-Sided Tape Inside the Cork Lid
Attaching double-sided tape to the inside of the cork lid is an easy way to trap adult gnats. As they crawl or attempt to fly, they’ll stick to the tape, reducing their numbers.
3. Reduce Moisture & Let the Substrate Dry Slightly
Since fungus gnats lay eggs in moist soil, controlling humidity is key:
✔ Allow the top layer of soil to dry out before misting again.
✔ Reduce watering frequency to prevent excessive moisture build-up.
✔ If possible, leave the terrarium open for a few hours daily to improve ventilation.
4. Introduce Natural Predators (Springtails and Isopods)
If your terrarium already contains springtails, they can help control fungus gnat populations by outcompeting larvae for food. However, if you plan to use hydrogen peroxide, skip this method, as it will harm springtails as well. Discover our selection of isopods and springtails which can help you get rid of the fungus gnat here.
5. Hydrogen Peroxide Treatment (Use With Caution)
Hydrogen peroxide can kill fungus gnat larvae, but it must be used carefully:
⚠ Dilute 3% hydrogen peroxide with water (1:4 ratio) before applying.
⚠ Only use this method if your terrarium does NOT have springtails, as it can kill them too.
⚠ Be mindful that adding liquid could lead to overwatering, which may worsen the problem.
6. Temporarily Place a Small Butterwort (Carnivorous Plant) Inside
For larger terrariums, a small Butterwort (Pinguicula) can be temporarily placed inside to catch fungus gnats. These carnivorous plants attract, trap, and digest gnats, reducing the adult population. After a few days, remove the Butterwort to avoid disrupting the ecosystem. Browse natural fungus gnat killers, carnivorous selection here.
How to Prevent Fungus Gnats in a Terrarium
Once you’ve eliminated fungus gnats, follow these preventative steps to keep them from returning:
✅ Monitor moisture levels – Avoid overwatering and let the top layer of soil dry slightly before misting.
✅ Remove decaying plant material – Decomposing leaves provide an ideal breeding ground.
✅ Use springtails – These beneficial microfauna help prevent gnat larvae from thriving.
✅ Check for early signs – If you see black tiny flies in your terrarium, act quickly to remove them before they multiply.
Final Thoughts
If you notice black tiny flies in your terrarium, don’t panic! By removing adult gnats manually, using double-sided tape, controlling moisture, and introducing natural solutions like Butterwort or springtails, you can eliminate them without harming your plants.
With proper care and prevention, you can keep your terrarium healthy and pest-free. 🪴
