Water Quality - Unit 4

pH (Hydrogen Ion Concentration)

Purpose: The purpose of this experiment is for students to gain experience in altering the pH of water and to observe how goldfish respond to different hydrogen ion concentrations in their environment.

Materials:

    • 3- goldfish
    • 3- 1L beakers (graduated)
    • pH measuring kit (test kit)
    • pH Adjuster aquarium pH adjustment chemical that increases pH
    • pH Down aquarium pH adjustment chemical that decreases pH

Note: Read all of the instructions before proceeding!!

Setup:

1.) When beginning the activity, fill each beaker with 1000 mL of the neutral water from the aquarium. Also, label one beaker Low pH, one High pH and one Control.

3.) In the Low pH beaker, the water needs to be adjusted to a pH between 5.5-6.0. Add the indicated amount of pH Down. Next, stir the water and allow it to sit for 30 seconds. Then measure the pH. If the pH of the Low pH solution is not at the target range, add more pH Down and measure again. Repeat this process until target pH is reached.

4.) In the High pH beaker, the water needs to be adjusted up to a pH between 8.0-8.5. Add the indicated amount of pH Adjuster. Next, stir the water and allow it to sit for 30 seconds. Then measure the pH. If the pH of the High pH solution is not at the target range, add more pH Adjuster and measure again. Repeat this process until target pH is reached.

5.) Do not change the pH of the water in the Control beaker, it should still be approximately 7.0.

Predictions:

6.) Make predictions about what will happen to the fish and record these predictions in the appropriate box in the student journal activity for this experiment.

        a. What is the predicted behavior of the fish in Low pH?

        b. What is the predicted behavior of the fish in High pH?

Observations of goldfish behavior:

7.) Remove 3 goldfish from the aquarium and place one each in the Low pH, High pH and Control beakers.

8.) The fish need to be left undisturbed in the beakers for 5 minutes to let them acclimate to the different pH of their environment.

9.) Select one of the following physical movements to monitor in every goldfish:

    • swishing of tail
    • flexing of mouth
    • flexing of gills
Each of these movements are normally performed by fish.  

10.) After the 5 minute acclimation time has passed, make observations on your fish.

Count the number of times each goldfish makes the selected movement during a 1 minute observation period.

Also, record any differences in the speed that the fish move, physical appearance, or behavior.

Record your observations in the Student Journal Activity sheet.
 
Note: Counting the number of times that the fish swishes its tail is probably the easiest measurement to make.

Discussion:

11.) Compare your results with what you predicted. Are the results what you expected? Are the behaviors of the experimental groups different from the control group?