This guide was designed to help teachers and students set up aquariums in their classrooms. Below you will find suggestions and links to assist you with this task. Please feel free to add or change the following teacher guide so it best fits your needs.
Before starting the aquarium project you may want to take time to establish the degree of prior knowledge your students have on the topic of aquatic ecosystems. This may be accomplished in a variety of different ways. You may want to lead a classroom discussion in which you ask students specific questions regarding ecosystems and aquatic environments. Or, you may find it more useful to have students respond individually or in groups to a series of specific questions formulated to assess their background knowledge of what is required to maintain a successful aquatic ecosystem. After this assessment you may ask your students to formulate questions for which they do not know the answer. These questions can serve as guidelines for inquiry during the aquarium project investigation.
Developing the Hypothesis - have students generate an educated guess as to what influences the addition of variable factors (gravel, algae, plants, snails, fish, time) will have on the quality of water in the aquarium. Ideally, before each variable factor is added, students will make a new hypothesis and analyze the impact of the preceding factors and decide on what action to take.
The procedure included in the student worksheet is an example of one you might want to use. You could have students develop a procedure for testing by posing a variety of questions to them such as “What do you think we should look out for as we perform tests on the aquarium environment?” or “How should we test the water?” or “When should we test the water, at what depth should we run the tests, and how shall we make observations?” From these questions, a table/chart could be generated to record all results. As the experiment proceeds, check for changes, and based on the data collected, ask students if any additional factors should be added or changed. Initiate student discussions on the reasons for their suggested alterations. Try to get them to recognize the process and the need for consistency in the methodology.
The initial test tank will not have added heat or light. This is for the purpose of approximating a “raw” environment from which the students will determine the necessary changes to create a viable, constant, aquatic ecosystem within the classroom.
Stress the importance of sampling techniques and test consistency to students. You should determine with them the depths at which they will take test samples. The proper use of a microscope and how to record accurate microscopic observations may also need to be reviewed.
Hydrometers used to test fluid density can be purchased in a catalogue or made by using clear plastic straws, modeling clay, sand, water and olive oil to make the scale. To construct the hydrometer, first seal the end of the straw with clay or sealing wax. Hold the straw upright in a beaker of water while you pour a small amount of sand into the open end of the straw. Add enough to stabilize the straw, but not enough to sink it. Carefully note the water line and label this point on the straw as 1.00 with a fine-tipped permanent marker, since the density of water is 1.00 g/mL. To provide another reference point, float the hydrometer in olive oil and mark the level it floats at, as this is 0.92, the density of olive oil (92% of the density of water - specific gravity is the ratio of a substance’s density relative of water.) Using these two points, you should be able to generate an approximate scale of specific gravity. Use student-made hydrometers to determine the specific gravity of the tank water in their aquarium.
Turbidity can be determined using a simple scale made from varying shades of colored pencils (or you can make sealed vials of dirt and food coloring of varying composition to approximate turbidity likely to be seen in the tank.) Your scale should be somewhat like: Level 1 - clear, Level 2 - partly cloudy (10-30%), Level 3 - non-living floating objects (<50%), Level 4 - nearly obscured (>55-90%), and Level 5 - obscured (91-100%). Make your comparisons using a small, clear dropper of tank water against a white background.
Several water quality tests will be made weekly such as nitrates, phosphates, pH, and dissolved oxygen in our version of the project due to kit costs. Although, if you have water quality test kits available which will allow you to make more frequent measurements, go for it!
Note any algal blooms/die-offs upon further observations of algal inoculate.
For many classrooms, contamination of the tank by trash or other objects thrown in by uncaring kids is an unfortunate possibility. A screen mesh can be constructed to protect your tanks. You may also consider storing tanks in an adjacent workroom or in an out-of-the-way area of the classroom. All of which may prove to be possible deterrents to that problem.
Questions have been development to encourage data analysis. You may find these questions useful when discussing various topics with your class or you may want students to include answers to these questions in their lab write-ups.
