How to Explain to Kids That Fish Breathe Oxygen

By Kathryn Hatter ; Updated April 18, 2017
Lessons about how fish breathe may fascinate kids.
Lessons about how fish breathe may fascinate kids.

Although fish swim underwater, it might surprise your child to learn that they breathe oxygen just as he does. With an engaging and informative science lesson about how fish live underwater, your child will have an important understanding of this wildlife concept. Make the learning experience even more interesting by including enjoyable activities that will help increase your child’s grasp of this idea.

Invite your child to take a deep breath and then exhale. As she does this, remind her that with every breath she takes, she is breathing oxygen. Tell your child that the oxygen she breathes travels to the lungs, where blood vessels transport the oxygen through arteries throughout her body, according to the KidsHealth website.

Show your child the fish swimming under the water and tell him that the fish’s body needs oxygen just like his body needs it. Encourage your child to share his ideas about how the fish gets the oxygen it needs.

Explain the way a fish takes in oxygen to your child. You might say, “As a fish swims, it opens its mouth to suck in water. The fish then pushes the water out through gills on both sides of its mouth. As the water moves through, the gills separate the oxygen present in the water so the fish’s body can use the oxygen.” Compare a fish’s gills to your child’s lungs to help her understand the similarities.

Describe a fish’s gills to your child to help him understand the respiratory process of fish. You might compare gills to thin membranes or even feathers, according to the Wonderopolis website. Tell your child that the gills contain blood vessels for transporting oxygen just like his lungs do.

Discuss oxygen in water with your child. Explain to her that for fish to get the oxygen they need from water, the water must be a healthy environment. Oxygen enters water from the atmosphere, from wind moving the water and from photosynthesis, according to professor Ruth Francis-Floyd, with the University of Florida Cooperative Extension Service. As the sun shines on water, photosynthesis occurs involving plants growing in the water. If water does not have optimal oxygen levels, because of an overabundance of algae, waste or decreased plant life, fish may not survive in the water.

Demonstrate how gills filter oxygen out of water. Place a coffee filter into a small metal strainer and position it over a large glass. Combine about 2 tablespoons of fine sand and 1 cup of cool water in another glass, shaking the ingredients enough to mix them well. Pour the water and sand into the metal strainer into the glass below and notice how the strainer separates the sand from the water. Tell your child that the sand represents oxygen, demonstrating how fish gills separate oxygen from water.

Things You Will Need

  • Live fish
  • Coffee filter
  • Metal strainer
  • 2 glasses
  • Fine sand

About the Author

Kathryn Hatter is a veteran home-school educator, as well as an accomplished gardener, quilter, crocheter, cook, decorator and digital graphics creator. As a regular contributor to Natural News, many of Hatter's Internet publications focus on natural health and parenting. Hatter has also had publication on home improvement websites such as Redbeacon.