I was also thinking about something like that... Or perhaps a larger tube with clear poly surrounding the UV light in the center to let multiple res's have their
nutrients pumped through it on the way to the plant or on the side with a second
pump.
I read that the UV light has trouble penetrating the glass and clear plastics... you would have to get a special glass or plastic to use from my understanding.
I have seen things where the UV light is actually set up in a way that the water is flowing over the light itself. (no splashing and constant contact prevents the fast temp change that cracks the glass)
I am still reading more into it, and will let you know what I find on that...