I am at the end of my battle with ostreopsis. I caught it early and made sure my N03 and P04 were elevated. 10-15 N03 and 0.05 P04. Manual removal by siphoning and filtering through a sock, change filter socks daily, lower light intensity and photoperiod, and dose MB7. This all slowly took the numbers down. I hooked up an oversized UV just 2 days ago (only ran when lights were out) and I can’t hardly see them anymore, comfortable enough to start raising light intensity. IMO the most effective were raised nutrients and UV