Most of those treatments are not 100% reef safe, even the ones that claim to be so.
If you have a nuissance algae problem, there is more NO3 and PO4 in your tank than what is being measured in the water (what are you using to measure NO3 down to that level, btw?). Testing the water only measures the nutrient concentrations available in the water, not what any algae has taken up. It's just as easy to have a tank with nuissance algae and have elevated NO3 / PO4 as it is to have a tank with barely measureable NO3 / PO4. To ultimately reduce the total amount of nutrients in the tank, removal of the nuissance algae is required. Otherwise, as any of it dies, is killed by a treatment, or is eaten, the nutrients are just recycled within the tank and made available again for more algae to grow.