STEM Club: Goldfish Lab

I have been teaching a science course over the past few weeks for local homeschool kids.  Though the course is designed for upper elementary kids (the target age is that of my own kids), the level of science experience and background knowledge varies. The only unifying characteristics are that they all have an interest in science and a passion for learning.

As a result, I have been struggling to squeeze in as much content as I can in the 90 minute class time. As expected, each activity is rushed and I know that the kids aren’t digesting the content as well as they could.  I thereby decided to slow down and focus on quality rather than quantity.  Seems so simple now that I can hardly believe I didn’t take this approach from the beginning.  The goldfish lab that we did last week was the perfect lab with which to slow down and focus on quality observations and data collection.

goldfish lab

Our focus this week was on the vertebrate class – bony fish. Rather than spend any time in class taking notes, I encouraged the kids to complete the vertebrate animal chart on their own. I wanted to use class time for the hands-on activity – this was how I had envisioned the class to begin with.

Fish belong to a larger group of animals called chordates and they make up a special group or class of the vertebrates called Aves. The vast majority of fish belong to the superclass Osteichthyes, the Latin word for bony fish.  With this age group, however, I didn’t go into detail about the taxonomy.

Generally, a scientist would do research or make an observation in nature before deciding upon an experiment.  I had chosen the experimental question for the group to tie it in to our curriculum but also to provide an opportunity to teach the scientific method.  We thereby used our prior knowledge and past experiences to develop our own hypothesis (which I encouraged them to write down in their notebook without sharing with one another so as not to influence anyone).

Goldfish Lab

Experimental Question

How does the temperature of the water affect the gill beats of a fish?


Answer the experimental question based upon what you know.  As you answer the question, provide a reason or explanation for your answer.  Why do you think the gills will beast faster/slower?


  • goldfish
  • small jar or glass beaker
  • larger beaker or container in which the small beaker will fit
  • thermometer
  • water
  • stopwatch
  • lab worksheet free download (optional)


  1. Place the fish in a small jar. Record the temperature of the water in your notebook.  (Room Temp)
  2. Count the number of gill beats for 1 minute.
  3. Repeat step #2 twice more.  Find the average number of gill beats for room temperature.
  4. Add ice water to the larger beaker. Place the small jar into the larger container.
  5. After a few minutes, record the temperature of the water in your notebook.  (Cold)
  6. Repeat step #2 and #3.  Find the average number of gill beats for cold temperature.
  7. Discard the ice water – perhaps you have a plant you could water?
  8. Add warm water (it doesn’t need to be hot, just enough to raise the temperature of the small beaker a few degrees) to the larger beaker. Place the small jar into the larger container.
  9. After a few minutes, record the temperature of the water in your notebook.  (Warm)
  10. Repeat step #2 and #3.  Find the average number of gill beats for warm temperature.


Record your data as you proceed in your notebook.  You may wish to create a table with a column for each trial and one for the average.


Look at your data and reflect on your experimental question.  Did the results surprise you?  What new questions do you have? Are there any possible errors? How could you improve this experiment if you were to do it again?


Those that complete the goldfish lab at home — please share your data by leaving a comment.  If we pool our data together, we can increase our sample size and thereby have a stronger conclusion.

About Eva Varga

Eva is passionate about education. She has extensive experience in both formal and informal settings. She presently homeschools her two young children, teaches professional development courses through the Heritage Institute, and writes a middle level secular science curriculum called Science Logic. In addition to her work in education, she is an athlete, competing in Masters swimming events and marathons. In her spare time she enjoys reading, traveling, learning new languages, and above all spending time with her family. ♥