Terrarium Care Guide
Free Care Guide
Terrarium Care Guide
Everything you need to keep your Blue Squid terrarium thriving, written by qualified horticulturist Zoe Carlini.
Based on years of professional experience. Updated for 2026.
In This Guide
- Closed Terrariums – the self-sustaining ecosystem
- Open Terrariums – succulents and air plants
- Light & Placement – where to put your terrarium
- Troubleshooting – common issues and quick fixes
- FAQ – your questions answered
1. Closed Terrariums
A closed terrarium is a closed, self-sustaining ecosystem. Water evaporates from the soil, condenses on the glass, and drips back down. It is a miniature water cycle sitting on your shelf, and it is one of the most rewarding things to watch.
The Golden Rule
A healthy closed terrarium should rarely need watering. If you see light condensation on the glass in the morning that clears by afternoon, everything is working perfectly. That is exactly how it should look.
How Often to Water
Almost never. After Zoe builds and seals your terrarium, it manages its own water. Check regularly: if the soil looks dry or there is no condensation at all, add a small amount of water. You can always add more, but you cannot take it away if you add too much. That is it.
Ventilation
If you see heavy condensation that does not clear, open the lid for a few hours to let excess moisture escape. Then put the lid back on. This might happen once in the first week as the ecosystem finds its balance.
Warning: Do Not Over-Water
The most common mistake with closed terrariums is adding water when it is not needed. More terrariums are killed by overwatering than underwatering. When in doubt, leave it alone. You can always add water later, but removing excess is much harder.
2. Open Terrariums
Open terrariums do not have a lid, so they do not create humidity like a closed terrarium would. They do retain some water as they have no drainage holes like a plant pot, making them well suited to arid planting such as succulents and air plants that enjoy airflow.
| Terrarium Type | How to Water | Frequency |
|---|---|---|
| Succulent terrarium | A small cup of water | In warmer months when the substrate feels dry. Not at all in winter. |
| Air plant terrarium | Submerge in water for a few minutes, then take out and place upside down until the leaves have dried out so they do not rot | In warmer months, perhaps once per month |
Pro Tip from Zoe
Test the soil with your fingertip. If the top 1cm feels dry, water. If it is still damp, wait. Your terrarium came with proper drainage layers; that gravel at the bottom is not just decorative, it is functional and prevents root rot.
3. Light and Placement
All terrariums want bright, indirect light. Think of a spot that is well-lit but never gets direct sun hitting the glass. The glass acts as a magnifier and can cook the plants inside very quickly.
| Placement | Verdict |
|---|---|
| North-facing windowsill | Ok, may need better light in winter |
| East-facing window (morning sun) | Good, not great |
| Bright room, away from window | Perfect |
| South-facing windowsill (direct sun) | Too hot, will cook plants |
| Dark corner, no natural light | Too dark, plants will stretch and weaken |
| Next to a radiator | Too dry and warm |
Never Put in Direct Sunlight
Glass amplifies heat. Even 30 minutes of direct sun can overheat a closed terrarium. Always choose bright, indirect light. A well-lit room is ideal.
4. Troubleshooting
Something not looking right? Here are the most common issues and how to fix them quickly.
Yellow Leaves
Leaves turning yellow, soft, and dropping
Cause: Usually overwatering. Can also be natural leaf cycling.
Fix: If the soil is soggy, open the lid and let it dry for 24 hours. Remove completely yellow leaves with clean tweezers.
Mould or Fungus
White fuzzy patches on soil, wood, or plants
Cause: Excess moisture, or too much direct sunlight combined with poor airflow.
Fix: Open the lid for 24 hours. Remove any fungus areas with a clean cotton bud. If it returns, the terrarium is too wet; allow more drying time between ventilations.
Leggy, Stretched Growth
Plants growing tall and thin, leaning toward light
Cause: Not enough light reaching the plants.
Fix: Move to a brighter spot (still indirect). Trim back leggy growth with clean scissors and the plant will bush out from the cut point.
Heavy Condensation
Glass completely fogged, water dripping inside
Cause: Too much moisture in the system, too much sunlight, or too much heat.
Fix: Try taking the lid off as it might be the moisture level. If it continues, it could also be the location, for example too much direct sun or too near a radiator.
Still stuck? Zoe can help.
Send a photo via the contact form and Zoe will diagnose the problem and walk you through the fix. Care advice is always free for Blue Squid terrarium owners.
Autumn & Winter
- Growth slows naturally; do not worry if things look quieter
- Central heating dries indoor air; open terrariums may need slightly more water
- Move closer to windows for maximum daylight (shorter days)
- Keep away from radiators, underfloor heating vents, and draughty doors
5. Frequently Asked Questions
How long do terrariums last?
With proper care, closed terrariums can last for years, even decades. The oldest known terrarium was closed for over 40 years. Zoe is always available for ongoing care advice at no extra cost. See our full care instructions page for more details.
Can I open my closed terrarium?
Yes, briefly. If you need to trim a plant, remove a dead leaf, or adjust something, open it and put the lid back on.
My terrarium has tiny bugs. Is that normal?
Small springtails (tiny white jumping insects) are actually beneficial; they eat mould and decaying matter, keeping your terrarium clean. They are part of the ecosystem. Fungus gnats (small flying insects) can appear if the soil stays too wet. They often will disappear on their own, however you can use sticky Fly Bug Catchers.
Can I add decorations to my terrarium?
Small decorative items like miniature figurines, crystals, or natural pebbles are fine. Avoid anything metal (it will rust in the humidity) or painted surfaces (paint may leach chemicals). If adding a new plant, make sure it likes the same conditions as the existing ones; ask Zoe if you are not sure.
What plants are in my terrarium?
Zoe selects plants that will thrive together in the specific environment. Common choices for closed terrariums include fittonia (nerve plant), ferns, peperomia, and living moss. Open terrariums often feature succulents, air plants. Check our care instructions page for plant-specific guidance.
Something has gone wrong. Can Zoe help?
Send a photo via the contact form and Zoe will diagnose the issue and talk you through the fix. Ongoing care advice is always free for Blue Squid customers.
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