My goal for this project is to make a closed ecosystem in a bottle. I want to learn the cycle of the nutrients and how they move in the ecosystem. I want to make this ecosystem while using only a few resources.

Step 1: What Is a Closed Ecosystem Compared to a Open Ecosystem

The ecosystem I am trying to make is a closed ecosystem.

A closed ecosystem is a self replenishing ecosystem which life can be maintained without external factors or outside aides.

An open ecosystem is when both matter and energy are exchanged between the system and its surrounding environment.

Step 2: Components of My Ecosystem

The Materials I used were:

2 liter clear soda bottle

Pond water from a local pond

The Components of my ecosystem were:

2 Fish (Guppies)

Plants (Anacharis)

Rocks

Decomposed stick and leaves

Step 3: The Design Process/Methods

Here is the design process and methods I used to create my closed ecosystem:

Gathered my materials
Cleaned out the 2 Liter soda bottle
Went to a local pond to collect pond water
Let the pond water sit in my house for 24 hours to make sure the water was room temperature
Collected rocks, stick and decomposed leaves
Washed the rocks to remove any chemicals that may be on them
Added the rocks, sticks and decomposed leaves to the bottle filled with pond water
Added the anacharis to the pond water
Carefully transferred the fish to the ecosystem

Step 4: Resources

I used the videos above and the website below to help me learn about closed ecosystems.

https://www.thegeoexchange.org/carboncycle/project...

Step 5: The Building Process

Here are the pictures of the steps in my building process

After I cleaned out a 2 liter soda bottle, I went to a local pond and collected pond water. Here is a picture of me filling the soda bottle up with pond water.
After I collected the water, I let the pond water sit for 24 hours in my house to bring the water to room temperature.
Next I went outside and collected rocks. Here is a picture of me with the rocks I gathered from my yard.

In the next picture, I washed the rocks to make sure there were no chemicals on them so the chemicals could not harm the fish from inside the ecosystem.
After the rocks were washed I placed them into the soda bottle filled with pond water
In the next picture I am taking the anacharis plant and placing it into the soda bottle.
Finally, I transferred the two fish carefully into the soda bottle, which is now the ecosystem.

Step 6: My Observations

My ecosystem works because the plants will eat nutrients. The fish then eats the plants and the process starts over again. The plants take in carbon dioxide and then release oxygen, which the fish breaths in that oxygen and they release carbon dioxide.

In the pictures I put it near the window because It would get the most sunlight for my ecosystem

When I first built my ecosystem, I saw tiny microorganisms floating in the water. These organisms are no longer there. I am assuming the fish ate these organisms. If this is a fully functioning ecosystem, I would think there would be more microorganisms floating around for the fish to feed on.

Another observation I saw was that the plant was moving up and down in my ecosystem. I am assuming maybe it is because of the density of the plant with the nutrients in it and without it. When it was at the top it was less dense than the water. But when it was at the bottom it probably had the nutrients inside and was more dense than the water.

One observation that I also saw was that the water got more clearer during the time. It might of been because of the fish eating the stuff inside of it. It is like the microorganisms with the fish but i'm not entirely sure. It might be because the plant filtered the water so it can get to the nutrients to fed the fish.

Another observation I saw during the time was that when I put it near the window the plant seemed to expand but when I put it away from the window it seemed to bunch up. I think it expanded when I put it near a window is because it was getting nutrients from the sun. But when I put it away from the window it bunched up because it probably wasn't getting enough nutrients.

One more observation I saw was that the rocks were letting off black microscopic stuff into the pond water. I think it was chemicals from outside but was not sure. If it was I could of cleaned them off better. I dont know but the chemicals could of harmed the fish.
The last observation I saw was that the fish where swimming fast sometimes but then not others. This could of been because they were hungry so they where trying to find food. After they were not swimming fast because they got food from any other microorganisms or the plant.

Here are some other video observations I made of my eco system.

Step 7: Additional Information on My Ecosystem

How an ecosystem works:

Gas exchange in a soda bottle ecosystem

The plants take in carbon dioxide. That plus the nutrients and sunlight through the process of photosynthesis produces oxygen. The animals breath in the oxygen and breath out carbon dioxide

Nutrient cycling in a soda bottle ecosystem

Plants absorb chemical nutrients from the soil. The plans get eaten by the animals. Animals produce waste which decomposes and released nutrients back into the soil

Water cycling in a soda bottle ecosystem

Water is consumed by both plants and animals. This is excreted, purified and reused to do it again.

Carbon cycling in a soda bottle ecosystem

This is when the plants take the carbon dioxide and use it to make food. The animals eat the plants and store the carbon until it is released.

Step 8: Results

Overall it worked fairly well and was a success. Something I would change if I did it again, was the amount of plant I used in my ecosystem. I would've changed this because I think it interrupted the cycle of the nutrients. Another thing I could have changed is that I would of added more decomposed sticks and leaves. I think it would do fairly well as time progresses because the cycle worked very good during the time I used it so I believe it would work fairly well as time progresses.

Step 9: Conclusion

Overall it was a fun project. I would definitely recommend this project for all ages and anyone who is interested in learning about ecosystems.

From creating my ecosystem, I learned what a closed ecosystem is and how it works. I was surprised that the fish could live without fish food and were benefiting from the ecosystem and were getting their nutrients from the plants.

I also learned about symbiotic relationships in a soda bottle ecosystem. In my ecosystem, I believe it was a mutualism relationship. This is where both partners benefit. Both the fish and the plants were benefiting from each other.

If I made another ecosystem I would maybe use a larger bottle and not as big of a plant, so the fish had more room to swim around. I also needed to add fish food as it wasn't clear to me if the eco system was providing enough food for the fish.