Test polyethylene tubing

I tried out my idea of illuminating the polyethylene tubing and want to make sure a 12-inch spacing will look good enough. I quickly threw a test rig together and found the red clear LED's drop 2.2 volts, so the red LED needs a 340 ohm resistor for 20 mA with a 9-volt source. The red was adequate at a 12-inch spacing, throwing light about 3 inches down the tube — testing with brighter LED's should yield more perceived distance.

Standard red, focused LED's in polyethylene tubing