You need to find out what is causing the problem first. Some foods are full of nitrates like those little cubes they really need to be thawed and rinsed before using and flake foods also have nitrates. Lights out will help kill the algae but it won't stop it from reoccurring and it won't hurt your fish. Don't scrub your rocks off in your tank all that will do is spread it. Take the rocks out and scrub them in and then rinse them you can use water that you would normally dump out for that adding a little peroxide in the rinse will only help with certain algae. I found it did very little for red turf algae but does a great job on bryosis. What type of algae are you dealing with? Are you using RO
water? How old are your bulbs?
Have you considered that the missing fish might be causing the algae? If you have a CUC you might not find the fish.
The only thing that the peroxide hurt was the bristle worms and brittle stars when I used a very high concentration. I didn't use it directly on anything but mushrooms as far as coral goes but it didn't hurt them.