---
title: Algae in a terrarium | Glass Jar Garden
description: Algae / cyanobacteria film on glass: A green film on the glass where light hits a wet jar.
url: https://glassjar.garden/guide/moulds/algae-cyanobacteria-film/
---

Moulds and films

# Algae / cyanobacteria film on glass

A green film on the glass where light hits a wet jar.

## Care

- Air humidity: 90 to 100%

- Temperature: 15 to 32 °C

## Description
Strictly speaking this is algae and blue-green bacteria, not a fungus. On glass it is only cosmetic, but slimy blue-green to black sheets can smother moss. Shorter days, less light, distilled water, no fertiliser and a few snails keep it down.

Also called green glass film, blue-green slime, black beard film.

Estimated, where sources were thin: spread_cm_per_day; temp_c; terrarium-specific source.

## Sources

- [en.wikipedia.org/wiki/Cyanobacteria](https://en.wikipedia.org/wiki/Cyanobacteria)
- [en.wikipedia.org/wiki/Green_algae](https://en.wikipedia.org/wiki/Green_algae)

[Grow it in a jar](https://glassjar.garden/?guide=moulds/algae-cyanobacteria-film)

[Blue-green mould](https://glassjar.garden/guide/moulds/penicillium-blue-green-mould/) · [All moulds and films](https://glassjar.garden/guide/moulds/)