If you go 25 then you need to speed up the gph. If you get a 20w then you need to slow it down. The slower the better as the bulb has more time to kill the ich in the column
Edit*** I mean the water going through it
It will kill the ich that goes through it but not the ones that don't. UV can be helpful but it won't cure a whole tank of ich.
__________________ 180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40bREEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.