Water Quality - Unit 2


Teacher’s Instructions

Purpose: The purpose of this experiment is to help the students appreciate the response of goldfish to different temperatures.

Materials for the class:

    • 40 liter aquarium
    • Bag of ice

Materials for each group:

    • 3 goldfish
    • 3 - 1000mL beakers
    • 3-Thermometers
    • 2-Large plastic tubs (37 cm x 31 cm)

Note: Read all of the instructions before proceeding!!

Suggestion: When designing this experiment we had in mind that you, the teachers, would divide the class into groups. This experiment is designed to be flexible given each teacher’s available supply of fish, beakers, etc. So, you may modify our setup given your number of students and available resources. However, step 13 requires that there be at least 4 members in a group (3 to observe and 1 to time.)

Teacher Setup:

1. Fill all three of the beakers with water from the aquarium that the goldfish are in. Fill each one to a level where the water is about 1 inch from the top of the beaker.

2. With masking tape and a marker, label one beaker "Hot", one beaker "Cold", and the third "Control".

3. Fill one plastic tub with ice, until it is almost full. Then add water to it until the water is about an inch below the rim of the tub.

4. Fill the other tub with hot tap water until the water is about an inch below the rim of the tub. The water must be very hot, so be careful!

Note: If the water from the tap is not hot enough, you may have to heat it up with a microwave or stove.


5. Have students make predictions on what will happen to the fish in the Hot and Cold environments.

          a.) What is the expected behavior of the fish in the colder water?

          b.) What is the expected behavior of the fish in the warmer water?

Note: Make sure the students know the Control group concept (in this case, the beaker with room temperature water). The control group is how they will determine if the fish in the Hot and Cold containers behave differently. They will not make predictions on what happens to the control group.

Student Setup:

6. Have the students place the Hot beaker in the tub of hot water and the Cold in the tub of ice water. The water in each tub should be at a level high enough that most of each beaker is submerged. The third beaker is to be left at room temperature (this is the Control beaker).

7. Have the students place a thermometer in each beaker. Instruct them to stir each beaker, to make sure all of the water in the beaker has a uniform temperature. They can use the thermometer to stir the water, but remind them to check the temperature of the water periodically. When the temperature approaches the indicated range for each beaker, they will have to watch the temperature more closely to know when to take the beakers out of the tubs.

8. The desired temperatures for each beaker are:

  • the Control beaker’s temperature should be between 20-25 º C
  • the Cold beaker’s temperature should be between 10-12 degrees º C
  • the Hot beaker’s temperature should be between 37-40 degrees º C.

9. When the water in the beakers reaches these temperatures, have the students remove them from the tubs of ice/hot water. Have them record the exact temperatures of the water in each beaker.

Note: This may take 20-30 minutes because water takes a long time to reach the desired temperature. Make sure that the water in the beakers has stabilized at this temperature; if not, the temperature in each beaker may continue to rise (or fall) after the beaker has been taken out of the tub. If the temperature is not stabilized, you could kill the fish.

10. Have the students place one fish in the Control, Cold and Hot beakers once the temperature of the water in the beakers has stabilized and as soon as possible following removal of the beakers from the water baths!!


11. After 5 minutes have elapsed, have the students make observations on the behavior of the fish. Is there a marked difference in the speed that they move? Is their behavior different? Is there a difference in their physical appearance?

12. Pick one of the following physical movements to monitor for every goldfish:

  • swishing of tail
  • flexing of mouth
  • flexing of gills
Each of these movements are done by the goldfish at a measurable rate in a normal environment.

13. Have one student count the goldfish’s movements in the Control, Hot and Cold beakers and have one group member serve as the timer. Count the number of times the goldfish makes this movement over the period of 1 minute. Record the rates and compare them.


14. Have students compare their results with what they predicted. The results will be based on any physical changes observed. Are the results the same as their predictions or are they different? Is the behavior of the fish in the hot and cold water different from the control group?

15. As a class, discuss the results. If any effect was (or wasn’t) seen, discuss what happened and how the fish was affected. If there was no marked effect, discuss why none was seen and what could be done next time so that an effect could be seen (e.g. more extreme temperatures or more sensitive organisms).