i will admit, i do not believe that the UV is GOOD for my shrimp, and could possibly harm them in the long run. im too much of a curious bastard to not try it though. once i get a "what if" question in my head, im compulsive about answering it.
UV can be completely blocked within the first few centimeters of water or it can penetrate many meters into the water. it all depends on what you have in the water that can reflect or absorb it. if you have dark stained water rich in tannins, forget about getting UV into your tank. if you only have dissolved salts though, you can probably get UV to penetrate deep.
the bottom of my tank still makes fluorescent objects light up, so im pretty sure the UV is reaching the bottom of the tank. even if it didnt, a lot of my shrimp spend a lot of time up near the surface anyway.
it may make no difference, but who knows? we wont discover new ideas without trying new things. ill have to play it out and see.
i can tell you this though, i had a group of fifteen amano shrimp in another tank for a couple months that never showed any color, but after a couple weeks in the UV tank, they are showing color and patterns. i need to set up a control before i can say that it is the UV that caused it. dont want to get ahead of myself.