Water Quality Lesson (Ages 5-8): “Fish Health, Algae, and Us”

Last month, a local girl scout troop emailed the Marine Science department at UNC Chapel Hill, asking if they could visit for a lab tour. Eventually the email made it to my inbox and I couldn’t pass up the fun!

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The girls wanted to learn about fish health. My lab focuses on phytoplankton (algae) ecology, so I thought this would be the perfect opportunity to teach about how fish, harmful algal blooms (HABs), and water quality all affect each other.

I started by having the girls brainstorm: What could cause poor fish health? Brainstorming acts as mock observation. (What do we already know/ what have we observed? What questions do we still have?) The goal was to lead them to scientific questions and informed hypotheses.

So, what could cause poor fish health? They began this exercise in the context of keeping fish in aquariums (ie. you have to remember to feed a fish, you have to clean the tank…) All of these ideas were valid, but we refocused our thinking to fish in a natural environment. They figured good water quality was important, but couldn’t quite get to what makes the water ‘dirty’ or unsuitable.

This was a perfect lead in to my activity: constructing an environmental model that mimics the causes of poor water quality. In my experience, kids love anything hands on and slightly messy, so this was perfect. I had them split into groups of 3 or 4, but this activity could be done in pairs as well.


Each group was first instructed to build their waterfront neighborhood. Rocks were placed on one side of the tub to be the foundation of the neighborhood.


I found that pond rocks were the best option for both cost and function. Aquarium rocks are far more expensive and typically smaller in size. This isn’t good for the activity because if the rocks are packed too tightly, it will be difficult to simulate run-off. Make sure you give the rocks a rinse before use. You want the added water to be clear.


Anything can be used to represent homes. I used popsicle sticks with monopoly homes hot glued to them. Have each group designate which house is theirs. They can draw a star on the corresponding popsicle stick if they wish. I found that not only did they enjoy constructing the neighborhood, but by they end they felt a certain level of investment in the creation. This is important because the next steps in the activity mimic the pollution of this pristine environment they’ve created.


Now for the fun part! Each group chose a Scientist #1, #2, and #3.
Scientist 1 used a small clear cup to take a water sample and placed it on the white place mat labeled t=0 (time=0 or “start”). I had the girls describe the water: did it look drinkable?


The girls were then told that one of their neighbors decided to use lawn fertilizer. They added colored sugar sprinkles (labeled ‘fertilizer’) to the area around the neighbor’s home.


They were then told that a spring rainstorm occurred, which they simulated using squirt bottles . During this process the color from the sprinkles bleeds into the water. Here scientist 2 took a water sample and placed it on the white place mat labeled t=1 (time=1 or “time 1”). I had the girls describe this sample, which was now dyed purple. This process was repeated with the pesticides, and scientist 3 was able to take the water sample at t=2.


After doing this twice the concept of run-off pollution, or the connection between ground water and bodies of water, was apparent to the group. I then had them use a soap dispenser pump to simulate their drinking well, which was inserted next to their home. How was the water quality of their own drinking water? It became clear that what their neighbors’ had done affected everyone and everything in the environment.


All of the directions for the activity can be prompted visually using the slideshare link below (slides 1-13). This covered water quality, but it’s crucial to connect the dots for the group, and relate it back to HABs and fish health. I did this with a series of simple animations (slides 14-19). Slideshare link: Water Quality Lesson (Ages 5-8): “Fish Health, Algae, and Us”

It was my goal to make the following points clear:

  1. Human actions such as using fertilizers and pesticides adversely affect water quality.
  2. Fertilizer can cause abnormal algal growth, which adversely impact fish. (Examples: a. Suffocation of fish b. Toxins poison fish)
  3. Pesticides can cause birth defects or death of fish.

chatoceros_imageImage Courtesy

To conclude their visit, I gave the girls a tour of our laboratory facilities and let them look at some of our algal cultures, like this Chaetoceros sp. (above), with a light microscope.

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Water Quality Lesson: Fish Health, Algae, and Us

  • Difficulty: Ages 5-8
  • Print

A hands-on environmental modeling activity to show how humans impact fish health.

Materials (per group)

  • 1 plastic tub (clear)
  • 1/2 volume of tub, pond rocks
  • 1 squirt bottle
  • dyed sugar sprinkles (2 colors)
  • 4 clear sampling cups
  • 1 soap dispenser pump
  • 3 popsicle sticks
  • tap water source


  1. Place pond rocks on one end of tub. Insert popsicle sticks into rocks to represent homes.
  2. Add water. Take first water sample in sample cup.
  3. Use colored sprinkles to “fertilize” around a home. Spray with squirt bottle to represent rain. Take second water sample in sample cup.
  4. Use colored sprinkles to add “pesticides” around a home. Spray with squirt bottle to represent rain. Take third water sample in sample cup.
  5. Insert soap dispenser next to home to represent a well. Pump fourth water sample into sample cup.

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