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Elodea and Goldfish Featured science projectScience project video


This science fair project was performed to determine if an Elodea plant can grow faster when planted in aquariums occupied by goldfish. The experiment was done by growing Elodea in an aquarium with one, five and ten goldfish and also in a tank without any goldfish.


The Elodea plant will grow faster in the aquarium with goldfish. The greater the number of goldfish, the better the rate of growth.

Scientific Terms

Nitrate, nitrite, algae, photosynthesis


Plants in an aquarium

Aquatic plants add more natural beauty to a fish tank. They also help clean the water and reduce the growth of algae. However, conditions in the aquarium must be suitable for both fish and plant. The types of plants that can be introduced into an aquarium include rooted plants and floating plants.

Fish feed and produce waste daily. Aquariums normally have filters which help to clean and remove some of this waste from the water. Most of this waste is in the form of nitrates and nitrites. They are the same nutrients required by aquatic plants to grow. Therefore, having more plants in an aquarium can help to lower nitrate levels in the water. This also means less algae growth and less frequent cleaning of the tank.

The gills of fishes absorb oxygen from the water and produce carbon dioxide. Plants living in the water need the carbon dioxide for photosynthesis and growth. Aquatic plants produce oxygen which is needed for the fish’s respiratory function. Plants in the aquarium are also used as food and as places for fish to hide. This symbiotic relationship is beneficial to both fish and plants.

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Complexity level:
Project cost ($):
Time required:
1 hour to prepare, 7 days for observation
Material availability:
May be acquired from a pet store
Safety concerns: