Goldfish and Elodea Plant Growth
Medium
Do aquarium plants grow faster when goldfish share the tank? Goldfish produce carbon dioxide and waste that plants can use as nutrients.
You set up four identical fish tanks with three Elodea plants each. One tank has no fish. The others hold one, five, and ten goldfish. All tanks get the same light and filtration.
After seven days you measure each plant and calculate the average growth. Compare the four tanks to see whether more fish leads to taller plants.
Hypothesis
The hypothesis is that the Elodea plant will grow faster in the aquarium with goldfish, and the greater the number of goldfish, the better the rate of growth.
Science Concepts Learned
Photosynthesis
Plants need carbon dioxide from the air to carry out photosynthesis and make food. Goldfish in an aquarium produce carbon dioxide and waste that nearby Elodea plants can absorb. When more fish share a tank, more of that key ingredient becomes available. This experiment tests whether that matters: four identical tanks hold three Elodea plants each, with zero, one, five, or ten goldfish. After seven days under the same light and filtration, you measure each plant and calculate average growth to see whether more fish leads to taller plants.
Method & Materials
You will set up four fish tanks with the same amount of water, aquarium lights, and filters. You will measure the height of twelve Elodea plants and place them in the four aquariums. The first aquarium will not have any goldfish, while the other three aquariums will have one, two, and three goldfish respectively. After seven days, you will measure the height of the Elodea plants again.
You will need twelve Elodea plants, four fish tanks of the same size, sixteen goldfish, enough water to fill four fish tanks, a pack of fish food, four aquarium filters, four aquarium lights, and a meter-long ruler.
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See what’s includedResults
The results showed that the Elodea plants grew faster in the fish tanks that contained goldfish. The greatest growth was observed in the aquarium with ten goldfish, with an average growth of 36 mm.
Why do this project?
This science project is interesting because it shows how the presence of goldfish can affect the growth of Elodea plants. It also demonstrates the symbiotic relationship between fish and plants in an aquarium.
Also Consider
Variations of this science project include using other types of aquatic plants, such as Anubias or Sword plants, and repeating the experiment with different types of fish, such as Parrot fish.
Full project details
Additional information and source material for this project are available below.Related videos
These videos explain the science behind this project and demonstrate key concepts used in the experiment.
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