My tank had a nasty ich outbreak that started last month. This killed several of my fish including my most prized Regal Angel that was eating well (kala mo tang sa takaw). Could not use other methods since my tank has lots of corals already.
I tried using UV light as last resort and . . . surprisingly it works!
I hooked up 4 11watt UV lights to 4 of my 1" (ID) pipes from the overflow box before going to the sump. After just 3 days, the visible ich on my fish were gone by at least 50%. After 1 week, I could count the ich visible on some of the fish that still had ich, most had no visible spots. During the height of my ich infestation, all fishes had lots of ich, some really covered with spots especially in the morning before my wrasse & cleaner shrimps did their job.
Will probably run the UV for 1 month 24/7 then just run at night after 1 month.
Now my fish aren't scratching on rocks and moving happily as they did before and their bright colors are back.