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Closed Ecosystems

Hi, our names are Tyler and Andrew, and we are experimenting with closed ecosystems in a bottle. The difference between a closed and open ecosystem is the closed ecosystem needs the organisms to work together to get their food. When the open ecosystem is usually given the food.

Materials Needed

To make your closed Ecosystem you will need two soda bottles, duct tape, knife, scissors, small rocks, algae, microgreens, dirt, worms and guppies.

Cut the Bottle

Start by cutting about four inches down from the top of the first two liter bottle. Flip the top of the bottle you just cut upside down and put it into the bottom part of the bottle you just cut. Now your ready to start filling the bottle.

Making the Top Level

Now you will start making the plant biome. Take your second two liter bottle and cut the bottom of it and place it upside down into the second two litter bottle that you just cut the bottom off of.

Adding to the Level

We started by duct taping the two bottle pieces together. Then add water. (we did cold sink well water, but you can use any water) The water is a main contributor to the ecosystem. It will be the habitat to the fish and also water the plants. Once you have filled the bottom with water then add algae and the pebbles. The algae will feed the fish and make oxygen. Now you can add the guppies.


Now you will make a filter. The filter is used to hold back the soil but let the water evaporate into the plant and then make its way back to the water biome. We used paper towels and some duct tape. Take three layers of paper towels and wrap the paper towel around the top of the bottle, pulling it very tight. Then duct tape the paper towel to the bottle.

Making the Plant Layer

Place the bottle with the finished filter upside down in the water biome. The filter should be right above the water but not touching it. Add soil into the top of the second bottle with the filter. Plant the seeds or do what we did and transfer a plant you already have grown. The plant will make oxygen for the fish, the algae or any other organisms you may add. Make sure you water the plants because it takes a couple days for the precipitation to start working. Optionally, you can also put in some earth worms. We thought this would help the plants grow better and be healthier by putting more nutrients into the soil.


Now it's time to make it a closed ecosystem. Take the bottom of the second bottle and tape it upside down. This will help keep the precipitation in the bottle to water the plants. You have now created a self sustained ecosystem.

Extra Advice

When the sun hasn't shown for more than two days, we suggest you put a flash light or large light near the ecosystem. The light will act as a sun giving away energy.

How It Works

In picture one you can see the algae has grown rapidly creating lots of food for the fish. Unfortunately, after two weeks the filter started to get very soggy causing some dirt to fall into the water and making it cloudy. It did not seem to affect the fish or algae at all. As you can see, a couple worms got through the filter and fell into the water. They eventually died, but it did not impact the algae or the guppies.

In picture two you will notice there is a lot of condensation proving our ecosystem is working.

In picture three you see the plants are thriving and growing.

In picture four you see a worm enjoying the ecosystem.

In picture five we have the whole ecosystem view. Our ecosystem was a success.

The only thing I would change would be to make a more durable filter. However, even though the one we made didn't affect our ecosystem, over time the paper towel will completely disintegrate allowing the dirt to fall into the water. Everything in the ecosystem worked together from the fish all the way to the plants. A big thing we noticed was the precipitation was amazing.


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