There are calculations out there to figure out flow rates to combat protozoa. Slower flow = more contact time is what your looking for. I run a 57w aqua uv at an documented 380-400g per hour on my return setup, 120g display with a 25g sump. It keeps ich at bay, I have a sailfin Tang that's a 'canary' for it. I don't run uv for 7-14 days the sailfin will get a spot or two first.So on uv, I know flow plays a factor in what it does slower for one and faster for the other. Algea vs parasites. Do you know which is which. I have a 32w or better (have to look to be sure I run them on all tanks) that runs 24/7. And it is new as I only set this tank up a few months ago.