Using RO water helps reduce the growth of brown algae. Tap water being rich in salts and chemicals are the primary reason for algae along with higher nitrogen.
Algaefix helps keep your tank cleaner for longer, reducing the need of frequent water changes. But don't expect anything drastic. It takes few days to do its work and should be used strictly as per direction and avoid pouring it directly into the aquarium as your fish may come to the surface thinking food and consume a deadly concentration. Mix it in a cup of water and pour it in your aquarium evenly.
Update after few months. Even less than recommended dosage is proving deadly to my fishes. In the last application, couple of danios were on the ground gasping for breath to save them I had to do a immediate water change and move them to a different aquarium.
While it is effective in controlling algae of all forms, it is suggested to move all plants and fishes for couple of days to a separate aquarium and then apply. As of now I have lost 3 fishes and one plant but algae growth disappeared for 5-7 days post application, but it won't stop them from coming back.
Instead of using biocide my advise would be to stick to water changes and regulating feeding.