I have a 24W coming from a canister that has a flow of 94 gal
/hour. I have had fish in the tank for about 6 months and when I fist got a pair of green chromis, a few days later my clown and royal gramma(I only have 4 fish in the tank) showed some ich spots. After reading lots and lots, and coming across all the "perfect Hobbyists" that say quarantining prevents everything, I still went ahead and bought the uv
I can say that the unit I got(its called BOYU, its a chinese copy of the turbo twist, I spent $170 for the 24W) did make a difference on helping the fish fight back the disease. One thing is for sure: quarantine or not, one day something happens and ick will find its way in. It might not manifest the disease completely, but its there. The UV
WILL NOT prevent ick, but it will help you control it and allow your fish to fight it and live with it. My fish do not have any ick signs for months; they are completely fine. I do know ick is in my system. The UV
will kill all the ick that is swimming in the water, not allowing it to multiply uncontrollably to a stage that will overwhelm and kill your fishes.
Buy a good unit, with decent wattage for your tank size, reduce the flow to as much as you can in it and leave it to do its work. It doesnt matter if you wait 8, 10, 2 weeks now. Ick will find you if your system lacks something somewhere. For those that say that overkill on UV
will "kill" the good bacteria, dont worry about that. I have my tank crowded with corals and they are all open, and my readings are completely perfect.