Skip Navigation

Can Nutrients in Water Cause Harm?

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Judith Dresden, MS.


Conduct this activity as a class demonstration. Have students work individually to complete his or her own worksheet. 

Teacher Materials

  • 2 oz hay or dried grass 
  • Small container of fish food 
  • Small container of liquid fertilizer 
  • 1 gallon of spring water (or de-chlorinated tap water, see Setup) 
  • 1 1/2-gallon aquarium with lid 
  • 3 clear, soft drink bottles, 2-liter size

Materials per Student

  • Pen or pencil 
  • Copy of student sheet


  1. You will need a hay infusion kit or pond water to conduct this demonstration activity. To start a hay infusion, set up a culture in a small aquarium about a week before beginning the activity. Add hay to one gallon of spring water or de-chlorinated tap water. (Chlorine is added to tap water to kill microorganisms, so water straight out of the tap will not be effective in making “pond water.”) If you use tap water, it is very important to let it rest uncovered for 24 hours, so the chlorine will have time to evaporate. An added light source will encourage growth within your hay infusion, and also will help to limit the foul smell.

  2. As an alternative to making your own hay infusion “pond water,” you can use water that you and/or your students collect from a pond, ditch or stream. If you are collecting your own water, try to find a source in which green algae is floating.

  3. In addition to “pond water,” you will need 3 clear, 2-liter plastic soft drink bottles. Cut off the tops of the bottles and make cylindrical containers from the bottle bottoms.

Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698

Houston Endowment Inc.

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education