Terrariums are designed to be low maintenance, but a little care will keep yours looking its best as it grows and changes over time. Here you'll find advice on lighting, watering, airflow, condensation and caring for bioactive terrariums.

Most terrarium plants prefer plenty of bright, indirect light. Avoid placing your terrarium in direct sunlight, as the glass can trap heat very quickly and cause the plants to overheat.

A bright room away from direct sun is usually ideal. If natural light is limited, a suitable LED grow light can also be used. You may need to adjust the position over time if you notice plants stretching towards the light or losing colour.

Closed terrariums recycle much of their own moisture, so they usually need very little watering. The substrate should stay lightly moist rather than wet or waterlogged.

If your terrarium starts to look dry, add a small amount of water rather than soaking it. It's always easier to add more water later than to remove too much. Avoid watering on a fixed schedule and use the appearance of the plants, substrate and condensation as your guide.

Some condensation is completely normal in a closed terrarium and is part of its natural water cycle. You may notice more moisture on the glass in the morning or evening as temperatures change, which often clears as the day goes on.

If the glass stays heavily fogged or covered in large droplets for long periods, the terrarium may be too wet. Remove or open the lid for a while to allow some excess moisture to escape, then close it again once the condensation has reduced.

Closed terrariums don't usually need to be opened regularly. If the plants look healthy and moisture levels are balanced, it's best to leave the terrarium to maintain its own environment.

Occasional airflow can help if the terrarium is staying excessively wet, condensation isn't clearing, or you notice mould developing. In this case, remove or open the lid for a short while and allow some excess moisture to escape before closing it again.

Mould

A small amount of mould is quite common in a humid terrarium, particularly around new wood or decaying plant material. It will often settle down on its own, and springtails in bioactive terrariums will feed on it. If mould becomes persistent or widespread, check that the terrarium isn't staying excessively wet and allow some additional airflow.

Fungus Gnats

Fungus gnats can occasionally appear in terrariums and are usually more annoying than harmful. Avoid adding extra water while the terrarium is already very damp. If they persist, get in touch and I can help you work out the best approach for your terrarium.

Overgrown Plants

Plants will naturally grow and change over time, and some may eventually need pruning. Trim back overgrown stems or leaves with clean scissors, removing small amounts at a time. Fast-growing creeping plants can also be cut back if they begin covering slower-growing plants.

Changes in Plant Colour

Changes in colour can have several causes. Pale, stretched growth can suggest too little light, while bleached or scorched leaves can indicate too much direct light. Yellowing or deteriorating leaves can also be related to excess moisture. Remove dead leaves and consider whether the terrarium's light or moisture levels have recently changed.

Bioactive terrariums contain a clean-up crew, usually springtails and sometimes isopods, which help break down decaying plant matter and other organic material. They're a natural part of the ecosystem and you may occasionally spot them moving through the soil, moss or leaf litter.

Springtails generally find plenty to feed on within the terrarium. Isopods also benefit from leaf litter and decaying wood, as well as a small piece of vegetable every once in a while. This is also a good way to spot them, as they'll often come out to feed. Remove any food that is left uneaten for too long.

If the vegetable starts to grow a little mould, don't panic. Springtails feed on mould and will often gather around it. Small amounts of mould are normal in a humid terrarium, although persistent or excessive mould can be a sign that conditions are too wet.