The only way you will be dealing with them again is if you introduce them back into your tankJust for clarification, you have diatoms or dinoflagellates? Diatoms will typically go away on their own with time. If dinos, its a different matter. People have had some success with the following approaches.
1) Lights out for three days followed by reduced photoperiod
2) Dino X
3) Dosing peroxide
4) no water changes / dirty tank method
5) manual removal where possible
6) dosing metro
7) dosing vibrant
8) dosing bleach
I have not gone the bleach route yet, but have done various combination of the others to no avail. I may end up trying bleach but my concern is that even if I kill 100% of the dinos in the tank, I am just going to be dealing with them again in the future if I have system that is dino friendly. Maybe bleach is a long term viable dosing option, I don't know.
I will say that I have been dosing 30% hydrogen peroxide vs the 3% drug store variety, and it is much more effective. I just don't like it as a long term solution.