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Something's Fishy About That Fertilizer

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Did you know that when you use fertilizer in your garden, it can eventually reach a lake, stream, or pond? There are many different chemicals present in fertilizers. How will they affect the aquatic organisms in the ecosystem? In this science project you will get to find out!


Areas of Science
Time Required
Long (2-4 weeks)
This project will require approval from the Scientific Review Committee (SRC) if you use fish or any other vertebrate animal in your experiment.
Material Availability
Items are available from Approved Supplier Carolina Biological Supply Company. See the Materials section for details.
Average ($50 - $100)
This project requires adult supervision when handling and measuring liquid fertilizer.

Sara Agee, Ph.D., Science Buddies


Test the effects of liquid fertilizer on an aquatic environment containing small aquatic animals and plants.


Fertilizers are chemicals that are added to the soil to increase the growth of plants in yards, gardens, or large agricultural facilities. The effect on crops can be increased growth, but fertilizers can have a negative impact on surrounding organisms in the soil.

When a heavily fertilized field is irrigated, excess water can flow along the surface of the land and pick up the fertilizers. This is known as surface runoff. The fertilizer-rich surface runoff can directly flow into nearby streams, lakes, or ponds, like the one shown in Figure 1, below. Additionally, chemicals present in the fertilizer can also infiltrate the ground water system and contaminate it. This polluted ground water can also make its way into nearby ponds, streams, or lakes. What happens to the aquatic organisms that are present in the environment when chemical fertilizers are present? How do the fertilizers affect the organisms' ecosystem?

A picture of a pond
Figure 1. How are the organisms in aquatic environments, like this pond shown here, affected by the chemicals from fertilizers?

In this science project you will test the effect of liquid fertilizer on an aquatic environment. Each aquatic environment will be a mixture of small aquatic plants and animals. By adding different brands of fertilizer, you can test how they affect the environment. Which fertilizers are the best choice for the environment?

Terms and Concepts



This project was adapted from the Duckweed Bio-Assay protocol from Cornell University: At this site, you can find out the toxicity of different chemical compounds:
  • Habeck, M., 2006. Toxics, Eco-USA.net. Retrieved July 3, 2006.
Heavy metals are often used in agriculture as pesticides. Learn more about pesticide use and ecotoxicity from the Pesticide Action Netwrok (PAN): You can use this website to create a graph on your computer:
  • National Center for Education Statistics. (n.d.). Create a Graph. Retrieved August 19, 2008.

Materials and Equipment

Disclaimer: Science Buddies participates in affiliate programs with Home Science Tools, Amazon.com, Carolina Biological, and Jameco Electronics. Proceeds from the affiliate programs help support Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Our top priority is student learning. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know. Write to us at scibuddy@sciencebuddies.org.

Experimental Procedure

  1. Rinse each container thoroughly with water. Do not use soap because it can coat the plastic container and may be harmful to the organisms in your experiment.
  2. Assign a number (from 1 to 3) to each fertilizer you use. Use a permanent marker to label the fertilizers' bottles, or just write the numbers you assigned in your lab notebook.
  3. Label each container "1," "2," or "3" with a permanent marker. Also label one container "Control."
  4. In your lab notebook, make a data table like Table 1, to record your data in.
  5. Use a graduated cylinder or metric measuring cup to prepare the solutions for each container according to Table 1. Prepare one container for each fertilizer, making sure the numbers on the containers match the ones you assigned to the fertilizers. In the container you labeled "Control," only fill it with distilled water, but no fertilizer, since it is your positive control. Use bottled distilled water, not tap water, because tap water may contain chemicals, like chlorine or chloramine, harmful to aquatic life.
Fertilizer Number Amount of Water
Amount of Fertilizer
Total Volume
pH Observations
1 975 mL 25 mL 1000 mL    
2 975 mL 25 mL 1000 mL    
3 975 mL 25 mL 1000 mL    
Control (distilled water only) 1000 mL 0 mL 1000 mL    
Table 1. Prepare your containers based on this data table. You will want to prepare one container for each experimental fertilizer group, and one container that only has distilled water in it (and no fertilizer) for your control. The amounts of water and fertilizer needed are given in milliliters (mL).
  1. Check the pH of each container with your pH test strips and record the data in your data table. Also record any observations about the fertilizer or container you put it in.
  2. Evenly distribute the aquatic animals into each container, putting at least 5 into each container. If you are using more than one type of animal, make sure there is the same number of each animal type in each container.
    1. If you are using Daphnia, you can use a watering pipet or medicine dropper to move them from one container to another.
  3. Put 3 to 10 plants into each container, depending on the size of the plant.
    1. For example, if you are using small duckweed plants, 10 is a good amount, while if you are using the larger Elodea plants, 3 plants in each container is a better amount.
    2. If you are using duckweed, make sure that each plant has a stem (the part sticking down).
    3. If you are using large Elodea plants, you can carefully cut them into smaller pieces, about one or two inches long, so it is easier to count their leaves.
  4. In your lab notebook, make data tables like Table 2 and Table 3. In Table 2, write down the total number of animals in each container. In Table 3, write down the total number of plant leaves in each container.
    1. Note: If you are using more than one type of animal or plant, you can make another data table like Table 2 or Table 3 and separately record each type of animal or plant in its own data table.
  5. Each day, for five days, write down your observations in your data tables. Specifically, count and write down the total number of animals that are alive in each container, and the total number of plant leaves in each container.
Fertilizer Number Number of Animals Living
Day 1 Day 2 Day 3 Day 4 Day 5
Control (distilled water only)          
Table 2. Each day, write down the total number of animals alive in each container. Note: If you are using more than one type of animal, you can make a second data table like this one and record each type of animal in their own data table. Put the name of the animal type in the title of the data table.

Fertilizer Number Number of Leaves on Plants
Day 1 Day 2 Day 3 Day 4 Day 5
Control (distilled water only)          
Table 3. Each day, write down the total number of leaves in each container. Note: If you are using more than one type of plant, you can make a second data table like this one and record each type of plant in their own data table. Be sure to correctly title the data tables.
  1. Graph your results.
    1. You can make line graphs by hand or on a computer using a program like Create a Graph and then print the graphs out.
    2. Make one line graph that shows the number of animals living in each container over time. On the horizontal axis (x-axis) put the time (in days). On the vertical axis (y-axis) put the number of animals living. Make a line for each container you tested, including the control.
      1. Note: If you tested more than one type of animal, you can make a separate graph for each animal type.
    3. Make one line graph that shows the number of plant leaves in each container over time. On the x-axis put the time and on the y-axis put the number of plant leaves. Make a line for each container you tested, including the control.
      1. Note: If you tested more than one type of plant, you can make a separate graph for each plant type.
  2. Analyze your results and see if you can draw conclusions about how the different fertilizers affected the animals and plants.
    1. Did one type of fertilizer affect the animals more than another type of fertilizer? What about the plants?
    2. Did the animals and plants respond similarly or differently to the fertilizers?
    3. Overall, which seemed to be the least toxic? Which seemed to be the most toxic?
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Global Connections

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.
This project explores topics key to Life Below Water: Conserve and sustainably use the oceans, seas and marine resources.


  • In this experiment you tested different brands of fertilizer, but what about different amounts of fertilizer? Try an experiment making different dilutions of fertilizer in your bowls. What are the exposure limits for each of the different organisms in your study?
  • Different fertilizers can have different chemicals in them. Do some research on the types of chemicals commonly found in different fertilizers. Based on your research, predict which chemicals might be more, or less, harmful on aquatic environments. Then repeat this experiment but specifically compare fertilizers with different chemicals in them to test your prediction. Is your prediction correct or incorrect?
  • Try these other Science Buddies experiments to test the effects of toxins on aquatic environments:


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MLA Style

Science Buddies Staff. "Something's Fishy About That Fertilizer." Science Buddies, 22 Sep. 2023, https://www.sciencebuddies.org/science-fair-projects/project-ideas/EnvSci_p017/environmental-science/fertilizer-aquatic-life?from=Blog. Accessed 5 Dec. 2023.

APA Style

Science Buddies Staff. (2023, September 22). Something's Fishy About That Fertilizer. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/EnvSci_p017/environmental-science/fertilizer-aquatic-life?from=Blog

Last edit date: 2023-09-22
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