Honestly, fighting the algae in a more natural way will provide better long term results. The algae is there for a reason, and that reason is elevated nutrient levels. Do you know what the nitrate and phosphate levels are in your tank? There are reef safe media available to help bring those levels down.
Manually removing as much of the algae as you possibly can, while incredibly time consuming, will be very helpful. In physically removing the algae from your tank, you are also removing any nutrients the algae took up. If you do this often and consistently, stock an appropriate clean-up crew, perform regular water changes using RO/DI, and not overfeed; you'll be surprised how quickly things will turn around. You may want to consider adding a refugium to grow macro algae to compete with the other algae for available nutrients, limiting the growth of the unwanted algae.
Chemical additives are in many cases just a band-aid. The reality is, that if you simply kill the algae with a chemical additive, the algae is still going to require manual removal, otherwise the dieing algae is just going to decay and release all of the nutrients it took up back into your tank.
Other alternatives include "cooking" your rock, which is method of storing live rock wet in complete darkness for weeks to months -- there are different ways of doing this and lots of info available on the web. Some people have pressure washed live rock to remove large quantities of unwanted algae, but you risk having to cycle your tank all over again. Either of these additional suggestions may or may not be feasible, depending on what's already in your tank in terms of livestock.
