---
title: Closed ecosystem simulator: an ecosystem in a jar
description: Simulate a closed ecosystem in a sealed jar: water, light, humidity, soil, plants, moss, springtails, isopods and mould, day by day. Build your own ecosystem and watch it run.
url: https://glassjar.garden/ecosystem-simulator/
---

Ecosystem builder

# Closed ecosystem simulator

A sealed jar is a small closed ecosystem: water, plants, soil, a cleanup crew and mould, with nothing added from outside but light. Glass Jar Garden simulates one day by day, so you can build your own and see whether it holds together.

[Build an ecosystem](https://glassjar.garden/)

## What a sealed jar recycles

- Water: plants breathe it out, it beads on the glass and runs back down to the soil.
- Food: fallen leaves and old soil rot slowly, releasing the carbon and nitrogen plants grow on.
- Waste: springtails graze mould, isopods and worms break down litter and rotting wood.
- Energy: light is the one thing that comes in. Too little and plants starve; direct sun cooks the jar.

## The real thing

The best-known example is David Latimer's bottle garden: a spiderwort sealed in a glass carboy in 1960, reported to have been watered only once, in 1972, and still growing decades later ([Wikipedia](https://en.wikipedia.org/wiki/Bottle_garden), [Snopes](https://www.snopes.com/fact-check/self-sustaining-bottle-garden-1960/)). The simulator's own checks rebuild jars like it: a nine-year carboy left alone stays alive, its tradescantia the biggest plant. [Checked against real jars](https://glassjar.garden/guide/how-it-works/checked-against-real-jars/) lists all fourteen.

## What is simulated

- [Needs and health: Each day every living thing scores its needs; health follows the score.](https://glassjar.garden/guide/how-it-works/needs-and-health/)
- [Death and hazards: Only hazards kill, each rising from zero at its threshold.](https://glassjar.garden/guide/how-it-works/death-and-hazards/)
- [Soil: Layers drain, hold water, feed plants and set the pH the roots feel.](https://glassjar.garden/guide/how-it-works/soil/)
- [Water: Soil fills to what it can hold; the rest drains to the drainage layer.](https://glassjar.garden/guide/how-it-works/water/)
- [Humidity and the lid: Sealed jars keep every drop; open jars lose water to the room.](https://glassjar.garden/guide/how-it-works/humidity-and-the-lid/)
- [Light: The day's light, brightness times hours, drives growth.](https://glassjar.garden/guide/how-it-works/light/)
- [Temperature: The jar follows the room, a little warmer under a lamp.](https://glassjar.garden/guide/how-it-works/temperature/)
- [Plants: Plants grow on light and food, share space, and stop at the lid.](https://glassjar.garden/guide/how-it-works/plants/)
- [Moss: Moss creeps from its edges in damp air and browns back when dry.](https://glassjar.garden/guide/how-it-works/moss/)
- [Critters: Each crew is a colony that grows to what the jar can feed.](https://glassjar.garden/guide/how-it-works/critters/)
- [Mould: White mould blooms on fresh organics and leaves; springtails eat it.](https://glassjar.garden/guide/how-it-works/mould/)
- [Care: Mist, water, vent and tidy, by hand or on a routine.](https://glassjar.garden/guide/how-it-works/care/)
- [Chance and forecasts: Two things are random; everything else repeats exactly.](https://glassjar.garden/guide/how-it-works/chance-and-forecasts/)
- [Checked against real jars: Fourteen jars their owners described online, rebuilt and run: all fourteen turn out the way the real ones did.](https://glassjar.garden/guide/how-it-works/checked-against-real-jars/)

## Build your own

Choose the glass, pour the layers, plant it, add the crew, then seal it and run time at a day a second. Some jars thrive for years; others rot, cook or dry out, and the simulator says why.

- [Beginner jar easy](https://glassjar.garden/starter-jars/beginner-jar/)
- [Moss jar easy](https://glassjar.garden/starter-jars/moss-jar/)
- [Paludarium lite hard](https://glassjar.garden/starter-jars/paludarium-lite/)
- [Carnivore bog medium](https://glassjar.garden/starter-jars/carnivore-bog/)
- [Desert bowl easy](https://glassjar.garden/starter-jars/desert-bowl/)
- [Cloche garden easy](https://glassjar.garden/starter-jars/cloche-garden/)
- [Wardian case medium](https://glassjar.garden/starter-jars/wardian-case/)
- [Mini forest medium](https://glassjar.garden/starter-jars/mini-forest/)

[Open the ecosystem simulator](https://glassjar.garden/)

Building a real one? Start with the [terrarium simulator](https://glassjar.garden/terrarium-simulator/) and the [layers](https://glassjar.garden/guide/terrarium-layers/).