---
title: Mould in a terrarium | Glass Jar Garden
description: White fuzz in a new terrarium is usually harmless and fades in weeks; springtails eat it. Which moulds matter, what sets them off, and how to stop them.
url: https://glassjar.garden/guide/terrarium-mould/
---

Guide

# Mould in a terrarium

White mould blooms on fresh organics and leaves; springtails eat it. Most new jars fuzz white in their first weeks, and it fades on its own. The one to worry about is grey mould on weak plants.

- New jars usually fuzz white in the first weeks.
- Fallen leaves and leafy or bark top dressings keep feeding it, and it creeps to the ground beside.
- White mould is harmless to plants.
- Springtails graze it down; without them it can cover a fifth of the floor.
- Grey mould is a disease of weak plants in still, damp, dim jars.

- Growth: 45% a day at full food

- Grazed: 25% a day per 1,000 springtails

- Most cover: 60% of a spot

## The moulds and films a jar can grow

- [Algae / cyanobacteria film on glass](https://glassjar.garden/guide/moulds/algae-cyanobacteria-film/): A green film on the glass where light hits a wet jar.
- [Blue-green mould](https://glassjar.garden/guide/moulds/penicillium-blue-green-mould/): Blue-green powder on food scraps and fruit.
- [Damping-off / root rot water mould](https://glassjar.garden/guide/moulds/pythium-damping-off/): A water mould in soggy soil that rots roots and seedlings.
- [Green mould](https://glassjar.garden/guide/moulds/trichoderma-green-mould/): White fuzz that turns green on wood and soil.
- [Grey mould](https://glassjar.garden/guide/moulds/botrytis-grey-mould/): Grey fuzz on dying leaves and soft stems.
- [Pin mould / bread mould](https://glassjar.garden/guide/moulds/pin-mould-rhizopus-mucor/): Fast grey fuzz topped with pinheads, on fresh organic matter.
- [Slime mould](https://glassjar.garden/guide/moulds/slime-mould/): A bright yellow net or foam that creeps over wood and vanishes.
- [Sooty mould](https://glassjar.garden/guide/moulds/sooty-mould/): Black film on leaves where sap-sucking insects have been.
- [White fuzzy mycelium (new-wood bloom)](https://glassjar.garden/guide/moulds/white-saprophytic-mycelium/): White fuzz on new wood and soil in the first weeks.
- [Yellow houseplant mushroom](https://glassjar.garden/guide/moulds/leucocoprinus-birnbaumii/): A little yellow mushroom that pops up from potting soil.

## Keeping it down

- Add springtails before or right after sealing.
- Pick dead leaves out; they keep feeding it.
- Fogged glass all day means too wet: open the lid for a few hours.
- Give weak plants more light rather than more water.

See how springtails and isopods compare in [springtails vs isopods](https://glassjar.garden/guide/springtails-vs-isopods/).

[Watch a jar mould and clear](https://glassjar.garden/)

## More terrarium guides

- [Closed vs open terrarium: Which to build, and which plants suit each.](https://glassjar.garden/guide/closed-vs-open-terrarium/)
- [Best plants for a closed terrarium: Plants that live sealed, easiest first.](https://glassjar.garden/guide/best-plants-for-closed-terrarium/)
- [Best moss for a terrarium: Mosses for closed and open jars, and what they grow on.](https://glassjar.garden/guide/best-moss-for-terrarium/)
- [Terrarium layers explained: Drainage, barrier, soil and top dressing, and what each does.](https://glassjar.garden/guide/terrarium-layers/)
- [Terrarium drainage: LECA vs gravel vs lava rock: Every drainage material side by side.](https://glassjar.garden/guide/drainage-leca-vs-gravel/)
- [Springtails vs isopods: The cleanup crew compared: what each eats and where it lives.](https://glassjar.garden/guide/springtails-vs-isopods/)