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Elodea and Goldfish Featured science projectScience project video


The materials required for this science fair project:

-    12 Elodea plants
-    4 fish tanks of the same size
-    16 goldfish
-    Enough water to fill 4 fish tanks
-    A pack of fish food
-    4 aquarium filters
-    4 aquarium lights
-    1 meter-long ruler


1.    For this science fair project, the independent variable is the number of goldfish in the tank i.e. none, one, two and three goldfish. The dependent variable is the average growth of the Elodea plants. This is determined by measuring and calculating the average height of the plants after 7 days. The constants (control variables) are the size of the aquarium, the amount of water in the aquarium and the amount of light received by the plants.

2.    4 fish tanks are filled with the same amount of water. The aquarium lights and filters are installed into the 4 fish tanks.

3.    The height of the 12 elodea plants are measured using a ruler. The plants are separated into 4 bunches of 3 plants each. The average height of the plants in each group are calculated and the results recorded in the table below.

4.    One bunch of Elodea plants are placed in each of the 4 aquariums. The 1st aquarium will not have any gold fish. The 2nd, 3rd and 4th aquarium will each have one, two and three goldfishes. The aquarium filter is switched on. The aquarium light is left on for 10 hours a day.

5.    After 7 days, the Elodea plants are removed from the aquarium and their average heights calculated again. The results are recorded in the table below.

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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: