Answer: 0.27
Population density of the species in water:
Population density of a species in the water is given by the expression,
Density =Given in the question,
Number of goldfish in the tank = 12
Volume of the tank = 45 cubic feet
Substitute these values in the expression,
Density =
= 0.267
≈ 0.27 goldfish per cubic feet
Therefore, density of the tank will be 0.27 goldfish per cubic feet.