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Lessons 5: How Clean Should an Aquarium Be?

Bacteria in an aquarium impact the amount of harmful substances present. Does changing the water and cleaning the filter affect the number of bacteria in the environment? And could this affect the overall health of the fish in the aquarium?

Doing the science

  1. Start the Aquarium Sim.
  2. Click on the "Bacteria" option on the left-side menu bar.
  3. Add 20 ppm of bacteria to the tank.
  4. Click on "View Status" on the left side menu bar to verify that the bacteria were added.
  5. Click on the bottom yellow water level mark on the left side of the tank. The water level will drop to this level in a couple of seconds.
  6. Click on the upper yellow water level mark on the left side of the tank. The water level will rise to this level in a couple of seconds.
  7. Click on the "View Status" icon on the left side menu bar and record the number of bacteria present in the aquarium.
  8. Repeat steps 5 – 7.

Do You Understand?

  1. How did changing the water level affect the number of bacteria present in the aquarium?


  2. What implications does the relationship you described in the previous question have on living organisms in the tank?