1. Controlled variable in an experiment means the variables that are not changed and are kept constant during each trial and when changing the independent variable.
In this experiment, the controlled variables are the aspects that are not changed each time when you change the temperature.
Therefore, examples of controlled variables in this experiment may include: the fish, the pH in the environment, amount of sunlight/light avaliable, amount of oxygen avaliable, etc.
2. According to the results given, suppose if you keep raising the temperature, the amount of breathe will keep increasing. This can be a bad idea because the fish may not be able to support so many breathes. In addition, as the temperature is too high, the enzymes in the fish may be denatured, and the metabolisms may be slowed down or stopped. This may kill the fish.
