This topic has been discussed before, but I finally got around to sketching the addition of an LED to the Hobo Tower.
The gentlemen who use the tower as a beach resort were complaining that it is too dark and a bit scary inside of the tower. One of the gents recently saw the movie Jaws through a hole in the fence at the local drive-in. So to keep the peace on my railroad, the tank now has blue mood lighting. The sketch below shows how I added a 10mm LED to the tank.
In actuality, visitors were missing the spectacle of the gentlemen bathing in the tower, but now the blue light gets their attention. I found it easy to reflect the light around the tank to the best advantage by gluing a piece of aluminum foil to the tip of the LED.