Big Fish, Little Fish

4.3 based on 4 ratings

Updated on Jan 18, 2013

Grade Level: 6th - 8th; Type: Marine Biology


Determine the effect of tank size on the growth rate of freshwater fish. The goals of this project are:

  1. To test tank size against growth rates in freshwater fish.
  2. To provide information that could improve the quality of pet care.

Research Questions:

  • Does tank size affect fish growth?
  • What is the optimal volume of tank space per fish?

Some people say that the size of a fish tank affects the size of the fish that live there. But many experts say it's a myth. This experiment is designed to scientifically test the theory that larger tanks produce larger fish. Oscars are good for this project because they are easily maintained and have fast growth rates.


  • Computer with Internet access
  • Color printer
  • Digital camera
  • Typical office/hobby/hardware/craft supplies (paper, poster board, glue, etc.).
  • One 25-gallon aquarium setup with related supplies (pumps, gravel, food, etc.)
  • One 10-gallon aquarium setup with related supplies (pumps, gravel, food, etc.)
  • Ten baby Oscars from the pet store.
  • All necessary materials can be found in or around your home, at local stores, or on ebay.

Experimental Procedure:

  1. Read overview of relevant topics (see bibliography below and terms listed above)
  2. Address all of the above terms and research questions.
  3. Search and print out interesting images relevant to your topic.
  4. Take photographs throughout the course of the experiment.
  5. Set up two identical bowls, each containing a half gallon of tank water.
  6. Place five fish in each bowl, then carefully weigh each bowl. Be SURE to equalize the water temperatures when transferring the fish. Failure to do so kills the fish.
  7. Set up both aquariums.
  8. Place the 5 fish in one of the bowls in the 10-gallon tank. Place the 5 fish from the other bowl in the 25-gallon tank.
  9. Maintain your tank setups with care.
  10. Carefully record all observations as the fish continue to grow.
  11. After about 8 weeks, place the fish from each tank again into two separate (identical) bowls, with EXACTLY ONE gallon of tank water in each bowl.
  12. Weigh each bowl and compare this to your previous measurements. Analyze your data.
  13. Interpret your findings in a detailed report.
  14. Include interesting photos, diagrams and models in your science fair display.

Terms/Concepts: Aquatic Plants; pH factor; Vivarium; Ich


Judee Shipman is a Bay Area Educational Consultant and professional writer of quality educational materials. Her recent writing credits include (a popular and entertaining website about states), and a book called The Portable Chess Coach (Cardoza, 2006), currently available in stores.

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