Answer:
Hypothesis is ''With the increase of algae in the aquarium, fish population decreases''.
Step-by-step explanation:
The main problem was that there is no need for 2 aquarium because there is no need for aquarium 1 which has no fish and aquarium 2 which has fishes but no algae. With the increase of algae in the aquarium, fish population decreases is the hypothesis for this experiment. Concentration of algae is the independent variable of the experiment because there is no effect on it in the experiment.