You are concerned about the rate of death in catfish your aquaculture operation in tanks that have a high amount of algae growth. You collect some of the algae and send it to the university to have it identified. You find that it is a blue-green alga called Anabaena. Anabaena is known to be toxic to fish. You design an experiment to test how much of the algae the fish can stand before they die. You obtain 6 large aquariums (all the same size) and fill them with water taken from a healthy catfish pond at your operation. You put each aquarium on the same bench in the laboratory, where the light and temperature values are identical. You let the water stand for one day before starting the experiment. In aquarium 1, you add 2 grams of algae and no fish. In aquarium 2, you add 20 small catfish and no algae. Aquarium 3 gets 20 catfish and 2 grams of algae, #4 gets 20 catfish and 4 grams of algae, #5 gets 20 catfish and 8 grams of algae, and aquarium #6 gets 20 catfish and 16 grams of algae. The aeration rate of each aquarium is identical. You make two observations at the same time each day for two weeks. You keep track of the numbers of fish in each tank that die. What is the problem? What is your hypothesis? What is the independent variable? What is the dependent variable?

Problem: How does the amount of algae (anabaena) affect or cause the number/rate of catfish death

Hypothesis: IF there is a high amount of algae growth, THEN the rate at which catfishes die increases.

Independent variable: Amount in grams of algae

Dependent variable: Number of catfishes that die.

Explanation:

A scientific experiment starts with an observed problem or a question which can be tested. In this experiment, the rate of death of catfish in an aquaculture due to the high amount of algae (anabaena) growth is observed, hence, it is the problem. It will be asked as a question: HOW DOES THE AMOUNT OF ALGAE IN A TANK CAUSE THE RATE AT WHICH CATFISHES DIE.

Formualting an Hypothesis is the next step of a scientific method. Hypothesis is a testable explantation or suggested solution to the observed problem or asked question. A hypothesis of this experiment can be: IF THERE IS A HIGH AMOUNT OF ALGAE GROWTH, THEN THE RATE AT WHICH CATFISH DIE INCREASES.

Next is to test the hypothesis by conducting an experiment. In an experiment, the independent variable is the variable that the experimenter changes or manipulates in order to bring about a response. In this experiment, the independent variable is the AMOUNT IN GRAMS OF ALGAE ADDED TO EACH AQUARIUM.

On the other hand, the dependent variable is the variable being tested or measured in an experiment. In this experiment, the dependent variable is the NUMBER OF CATFISH THAT DIE.