How to Build an Ecosphere

Written by emmalise mac
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How to Build an Ecosphere
A biosphere is a self-contained ecosystem--large or small. (biosphere image by Frédéric Georgel from

Biospheres are self-contained ecosystems that support plants and animals. Biospheres may be terrestrial, freshwater, combination terrestrial/freshwater, or marine. Although it may take a few tries and a bit of adjustment, in terms of the number and type of organisms, to create a balanced biosphere, the final result will be a self-sustaining system. Biospheres enhance the aesthetic of a child's room or classroom, provide hours of entertainment, and promote scientific thought. You can create your own simple bottle biosphere in a single afternoon with only a few basic materials found in your home or collected from nearby wooded areas and ponds or streams.

Skill level:
Moderately Challenging

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Things you need

  • 2-liter clear plastic bottles with caps (2)
  • Utility knife
  • Drill and drill bits
  • Cotton string
  • Small gravel
  • Soil collected from a wooded area
  • Leaf litter collected from a wooded area
  • Water collected from a pond or stream, with live organisms and algae
  • Sand or soil collected from the bottom of a pond or stream
  • Small shade-tolerant plant
  • Small aquatic plant
  • Small aquatic, algae-eating organisms (e.g., snails or fish)
  • Small twigs or other decorative ornaments

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    Biosphere Construction

  1. 1

    Rinse the 2-liter bottles thoroughly and remove labels. Remove any non-transparent stabiliser pieces from the bottom of the bottles. Replace the bottle caps and screw them on tightly.

  2. 2

    Cut around the top of one of the bottles approximately one inch down the straight sides below the neck to create a funnel-like biosphere cap and an aquatic reservoir.

  3. 3

    Cut around the bottom of one bottle approximately one inch up the straight sides of the bottle below the fluted base to create a terrestrial chamber. Discard the bottom piece of the bottle.

  4. 4

    Drill a hole through the centre of the bottle cap on the terrestrial chamber. The hole should be slightly larger than the diameter of your cotton string.

    Biosphere Setup

  1. 1

    Add pond or stream sand to the bottom of the aquatic reservoir. Also add pond or stream water to the aquatic reservoir to a depth of approximately six inches.

  2. 2

    Add a few algae-eating, aquatic organisms, such as snails or tiny fish, and aquatic plants to the aquatic reservoir.

  3. 3

    Cut a piece of cotton string two feet long and tie a knot in the middle. Soak the string in pond or stream water until fully saturated--approximately ten to fifteen minutes. Thread the string through the hole in the bottle cap on the terrestrial chamber so that the knot is in the bottle cap.

  4. 4

    Rinse gravel thoroughly with tap water. Invert the terrestrial chamber and add a layer of rinsed gravel two inches deep. Be sure you don't bury the cotton string. Coil the cotton string in a spiral around the chamber over the gravel.

  5. 5

    Add several inches of moist forest soil to the terrestrial chamber. Add a small amount of pond water to the soil if necessary. Plant a small shade-tolerant plant in the soil of the terrestrial chamber. Cover the surface of the soil with leaf litter containing small invertebrate organisms, such as springtails and pillbugs.

  6. 6

    Place the terrestrial chamber into the aquatic reservoir. The bottle cap should be above the level of the water. Remove a small amount of water if necessary. The cotton string should hang into the aquatic reservoir--it will act as a wick to provide water to the terrestrial chamber.

  7. 7

    Add twigs or other ornamental objects to the terrestrial chamber for visual interest. Place the funnel-like biosphere cap over the top of the terrestrial chamber and place the finished biosphere in a sunny location.

Tips and warnings

  • Hang your bottle in a window for easy viewing and access to sunlight.
  • Add a few limestone rocks, such as calcium rocks from an aquarium supply store, to the water to help adjust the pH.
  • Add a small amount (e.g., 1 tbsp) of pond scum to the water to kick-start algae growth.
  • Don't add too many snails to your ecosphere or they will eat all of the algae. Start with one snail and add more later if needed.

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