Title: pH and Fish

Discipline: Life Science

Ability: 7th Grade

NJ Core Curriculum Content Standards:

5.1 A, B   5.5 A, B

 

Objective:

Students will gain an understanding of what the pH level of a solution tells us.  They will learn that different fish species are adapted to different pH levels.  The students will learn the importance of monitoring the pH of their fish tanks.  Students will also gain practice using the aquarium test kits, which will be important for monitoring the water quality of the fish tanks.

 

Materials:

6 pH test kits

Aquarium pH increaser

Aquarium ph decreaser

Four, 1-liter containers to prepare the different solutions

8 squeeze bottles

 

Preparation:

4 different solutions should be prepared using the pH increaser or pH decreaser at the different pH levels listed on the handout.  The pH increaser should be used to bring 1 liter of water to 8.6.  The pH decreaser should be used to bring three other liters of water to pH levels of 6.5, 6.0, and 5.0.  Fill 2 squeezer bottles for each solution. These bottles will be used by the students when doing the pH tests.

 

Discussion:

Stress to the students that it will be important for them to understand pH when it comes to designing their fish tanks.

 

pH- How much acid is not in the water.  How much hydrogen is found in the water.  Hydrogen is a chemical that is found all over the earth.  The pH is a measure of the concentration of hydrogen ions in a solution or “the power of Hydrogen”

 

Acids- Hydrochloric acid, battery acid, vinegar             Bases- Bleach

pH scale- ranges from 1(acidic) to 14 (basic).  A change is one pH unit means a tenfold change in concentration.  Some fish can tolerate a range of 5 to 9.  Other fish cannot tolerate a change in one pH unit.

Acid Rain- When rain falls through the atmosphere the gases it contacts come into solution.  Air pollution from exhaust, factories, and forest burning increases the concentration of chemicals like sulfur and nitrogen in our air.

 

  1. What are some ways the pH of a stream or pond could be changed?

Acid Rain, pollution, and the type of soil the rain moves through before it gets to the stream or pone.

 

  1. What are some effects that pH has on aquatic organisms:

-         Affects breathing

-         Can cause stress, disease

-         Effects the reproductive cycle of fish

-         Affects the nitrogen cycle

  1. What would happen if you put a fish bought at a pet shop into a tank in your home with tap water?

Most fish at a fish store come from tropics in Brazil or Africa.  The ph of tap water is about 7.1.  This fish you bought at the fish store might not be adapted to this pH.  If this is used to an acidic environment than this pH would be too high.  If the fish is used to a more basic environment than this pH would be too low.

 

At pH values lower than 5.5 the rate of oxidation of ammonia by bacteria( Nitrosomonas) is reduced resulting in increased ammonium levels.  Studies of fish done in low pH water that the gills are damaged which results in breathing problems and death.

 

Activity:

Students should work in groups of 4.  Each group should have a test kit. We used Dry-Tab Dry Tablet test kit.  It is not necessary for each group to have all 4-water samples at once.  They can be shared between the different groups.

            Tell the students that each water sample is from a different body of water but the samples are not labeled.  Since the pH of the water body the sample was taken from is known, their job is to figure out which water sample is from which body. This can be done once they determine the ph of the water sample with the test kit.

 

Assessment:

This lesson went well in all of the classes.  When ordering the material for the fish tanks we did not take into consideration how many pH tablets would be used during this lesson.  This caused a problem when students were monitoring the water quality of their fish tanks.

            Teaching pH requires some chemistry background, which the 7th grade students did not have.  We had to simplify the lesson in order for the students to understand the basic concepts of pH.  When this lesson was done in the 8th grade physical science class, I was able to discuss the chemistry concepts necessary to fully understand why pH in important.