I agree, elbow greese is the best remedy. Scrape the glass, toothbrush the rocks, water changes to export nutrients, and drop the sock.well all your nitrates and phosphates are bound in the algae. start with scraping walls, siphoning small sections of sand and pulling algae from the rock(out of the tank) followed by 10-20% water change. Do it every 3-5 days. you don't want shock your corals with sudden change in parameters. I see one white skeleton already. also add small amount of bacteria from the bottle + sludge buster/tank refresh type bacteria to breakdown any organics. Do you use any filter sock? change it after half an hour to an hour of water change. i would avoid adding any chemical based additives.