What is Wrong with my Pond?

Keywords: Water quality, water chemistry, pH, hardness; Lesson Plan Grade Level: 6-8; Total Time Require: 1 class period – 45 minutes; Setting: Classroom

Goals for the Lesson:

  • Student will examine various pond water samples to identify levels of Nitrates, Ammonia, pH, hardness, and alkalinity.
  • Student will explain importance of water quality in order for a successful pond.
  • Student will identify steps needed in order to keep pond water safe for wildlife and plants.

Materials Needed:

  • Various samples of pond water collected preferably from students. (at least 4)
  • Eco Check 5 in 1 test strip for pond water (or similar test strips)
  • Pond Care ammonia kit (or similar)
  • Data sheet one per group

State Standards Addressed: Environment and Ecology - 4.3 – Environmental Health; Science and Technology – 3.2 Inquiry and Design; 3.4 Physical Science, Chemistry and Physics

Teaching model: Inquiry/Hands-On

Subjects Covered: Chemistry, Ecology

Topics Covered: Water quality, water chemistry


Split class into groups of about 3-4 students give them the following scenario: You are a new pond owner. Come up with at least 3 things you want from your pond.

Have a classroom discussion based on the group answers. Lead discussion on water quality. Incorporate students personal experience/background on testing water. Use the following background information as a guide. Water quality will play a role in whatever use you intend for your pond. Things like Nitrates, Ammonia, pH, hardness, and alkalinity all can affect the ponds quality. Let’s assume most of you are looking for the pond to be able to have fish like Koi. We need to review the basic tests that we will perform and what the adequate levels for a successful Koi pond would be.

Nitrates (NO3-)– which are found commonly in fertilizers can cause higher than wanted algae levels and plants in the pond. We are looking for a value less than 20 ppm. If levels are too high we may need to address the land management around the pond. Is there fertilizer running into the pond from surrounding areas? What can we do to fix that? (buffer strips around pond, limit fertilizing)

Hardness is a measurement of calcium and magnesium along with other minerals in the water. A hardness that is too high will have too much algae and hardness that is too low will have too little vegetation. Koi require somewhat harder water because it prevents the salts within fish to be diffused through their gills and lowers the stresses on the fish. We are looking for levels between 150 – 300 ppm. Different salt solutions (except table salt) can be added to the water to increase the hardness.

pH – (basics would have been covered in previous lesson) A pH test measures how acidic the water is. Water with a value lower than 7 is acidic and water with a value higher than 7 is alkaline. Anything between 6.5 – 9 is adequate for Koi. Algae blooms can greatly affect the pH and need to be closely monitored.

Alkalinity – Is the ability for the water to accept acidification without affecting the pH. For Koi ponds a value of 40 – 120ppm is acceptable. Values that are too low can be treated by adding lime to the water.

Ammonia – (NH4+ and NH3) It is caused by decaying organic material and fish waste. It can cause gill damage, stress and other diseases. Even low levels of ammonia can become quickly harmful. We are looking for levels under 0.1 ppm. If levels are too high there are bacteria additives for the water that must be mixed in to reduce the ammonia levels. In the groups the students should then begin to test the water samples and record the data on the data sheet. After completing the testing the group needs to decide which pond samples would be adequate for Koi and which would not.


Each student is required to answer the following questions after completing the lab. This part should not be done as a group.

  1. What determines a successful Kio pond? Give specific examples.
  2. Say you have tested a water sample and the Nitrate levels are too high. What is a possible cause for this and what can be done to correct the situation?
  3. How does chemistry play a role in testing and correcting pond water?

Literature/Sources Cited

Management of Fish Ponds in Pennsylvania, College of Agricultural Sciences – Penn State University

Water Testing your Pond

Eco-check test kit

Pond Care Ammonia kit


Bryan R. Fatzinger, Mount Nittany Middle School