Answer:
The Independent Variable is the variable or thing that depends on nothing, nothing can affect it, nor can it be changed by any other variables, in this case the Independent variable is the Fish tank, the fish tank depends on nothing, and will stay the same.
The Dependent Variable is the variable or thing that depends on one or more variables in the equation, it be changed by any other variables, in this case the dependent variable is the fish, the fish depend on the water in the tank.