I had a re-emergence of mainly Ostreopsis earlier this year and went with just the Green Killing Machine 9 watt (cheap) in-tank running on a timer for 8 hours/night in a 40 gallon tank.
That worked for me in that case -- just blowing dino strands off of soft corals at lights out and letting the UV run for 8 hours/night.
*cleared 'em up within a couple of weeks and I kept it running for 2 months just to be safe before removing the UV -- haven't seen any since then and it's been quite a few months