Water Quality - Unit 5
The purpose of this experiment is for students to gain experience in
altering the nitrate levels of water and to observe how goldfish respond
to different nitrate concentrations in their environment.
- 3 goldfish
- 3 - 1000 mL beakers
- Marker and masking tape
- Nitrate nitrogen measurement kit
- Dissolved oxygen measurement kit
Note: Read all of the instructions before
1. Fill all three of the beakers with water taken from the aquarium that
the goldfish are in. Fill each beaker with 1000 mL (milliliters) of water.
2. With masking tape and a marker, label one beaker High
Nitrates which will represent a high level of excess nitrates
in the water. Label a second beaker Low Nitrates,
which will represent a low level of excess nitrates in the water and
the third beaker, label Control;
this will represent approximately normal conditions.
Preparation of the Beakers:
3. Set the Control beaker aside.
No fertilizer pellets should be added to this beaker.
4. Add an amount of fertilizer pellets that will yield 2 parts per
million of total nitrate nitrogen to the beaker that is labeled Low
Nitrates. If you are not sure
how much fertilizer to add, ask your teacher for help with this step.
5. Add an amount of fertilizer pellets that will yield 10 parts per
million of nitrate nitrogen to the beaker that is labeled High
Nitrates. If you are not sure
how much fertilizer to add, ask your
teacher for help with this step.
It will be necessary to use the a laboratory scale to determine how many of the fertilizer
pellets (mass) to add to the beakers to make solutions with 2 and 10 parts per
million of nitrate nitrogen.
Determination of Nitrate Nitrogen Level:
6. Determine the nitrate nitrogen concentration of each beaker. To do this,
use the nitrate nitrogen test kit from the Water Quality test kit and
follow the directions carefully. The test kit will yield a measurement
in parts per million (milligrams of nitrate nitrogen / 1000 mL of water).
Wait ~ 3 weeks before introducing the fish into these beakers.
- 7. Make predictions on the behavior of each goldfish in the three
different nitrate nitrogen level solutions. Record these predictions in the Student
8. Take three of the goldfish currently in the aquarium (each group
takes three fish), and place one in each of the beakers.
9. Allow the fish to be undisturbed for 5 minutes
in each beaker. This period allows the fish time to acclimate to their
new environment. Be sure to note the time when the fish are placed
into the beakers.
Pick one of the following physical movements to monitor in every goldfish:
- swishing of tail
- opening/closing of mouth
- flexing of gills
- Each of these movements are done by the goldfish at a measurable rate
in a normal environment.
Note: It has been found that counting the number of times that the
fish swishes its tail is probably the easiest measurement to make.
10. After 5 minutes have
elapsed, make observations on the behavior of the 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, their physical appearance, or their general behavior.
- Record your observations in the Student Journal Activity sheet.
11. Compare your results with what you predicted. The results
will be based on measurements of either swishing of the tail,
opening/closing of the mouth, or flexing of the gills. Are the results
the same as the predictions or are the results different? Is the
general behavior different or the physical appearance of the
experimental fish different from the control group?