A small fish is 0.9 inch long. How many centimeters long is the fish, to the nearest tenth?
To convert inches to centimeters, we can use the conversion factor: 1 inch = 2.54 centimeters.
Therefore, the fish is 0.9 * 2.54 = <<0.9*2.54=2.286>>2.286 centimeters long.
Rounding to the nearest tenth, the fish is approximately 2.3 centimeters long. Answer: \boxed{2.3}.