I run the DEBARY 25w uv rated up to 1500lts.
If you go to their site and read up on the info you will see that set up correctly with right size and flow it can be very effective with ICH.
About 4 months ago we suffered our first ICH outbreak and lost 8 fish. It is impossible to catch and QT all our fish because we also run a 380g with a lot of tangs.
We let the remaining fish settle after the outbreak, installed the uv and 4 months later have restocked the tank. We have once again had a small outbreak of ICH that has showed up as a few dots, but not got any worse at all.
It says it will kill the free floating stage only, which will not rid you tank of ICH but will stop the multiplying stage.
We have now been ich free for 3 weeks after losing nothing and believe very much it was the UV that did it.
They are expensive units but I wouldn't buy any other brand as this does what it says 100% unlike some of the cheaper units.
So although we now have ICH in the tank, we have to learn to manage it and the UV goes a long way in helping.