Objective:
The student will be able to define pH, to explain how it affects the tank's water quality and be able to test the pH level in the classroom aquarium.
Materials Needed:
Background Information:
pH is the measure of acidity or alkalinity of water. Literally, it stands for the power of the chemical Hydrogen. The pH range for freshwater fishes can vary greatly, depending on where the fish are bred. Most tropical fish that will be kept in the Aquademics™ aquarium will thrive in a pH level of 6.8 to 7.6. A regular pH check of the aquarium water in the tank is mandatory, since fish will show signs of acid or alkaline damage at levels that are below or above the recommended levels.
Activity:
The pH of the water in an aquarium is measured on a numerical scale from 1 to 14. An acidic solution is created by a compound or substance that releases hydrogen ions (H+) when dissolved in water and measures lower than 7. A basic, or alkaline, solution is created when a compound produces hydroxide ions (OH-) when dissolved in water and has a pH measurement higher than 7. A neutral solution - neither acidic nor alkaline - has a pH of 7. Using examples of foods like vinegar or apple juice, remind students that they cannot see the acidity or alkalinity in a substance, but it does exist.
Ask students if they have ever been in a location where it seemed hard to breathe. Some examples might be a city with lots of smog, a day when it was extremely humid or being near an industrial plant that emitted a very strong smell. Allow students to reflect on these questions for a few minutes and write their answers on the board. Be sure to ask students if they could "see" the humidity or "see" the strong smell. Also, ask students if they know what the most important chemical element is in the air we breathe (most will know it is oxygen).
Ask students if they think it is important that their fish should always be able to "breathe" freely. Tell them that if aquarium water is too acidic or too alkaline, then the breathing ability of their fish will be greatly diminished and, in fact, could be extremely harmful to their fish. Remind them again that acidity and alkalinity are not visible to the naked eye. Students may be very surprised to learn that oxygen is an important element to help fish breathe, too.
Train all students on how to test the tank's pH level using the TetraTest® pH Kit according to the instructions found inside the box. Students can use the kit to test the acidity or alkalinity of some common household substances such as vinegar, apple juice, milk, lemon juice, bottled water or tap water.
Result:
Students will want to regularly monitor the pH level of the aquarium water within the tank so that their fish will always be living in the safest and healthiest ecosystem possible. (If the pH level is too high or too low, the kit suggests the appropriate remedy that would be available from a local pet store.)
Portions of this page reprinted courtesy of the National Aquarium in Baltimore