An easy and common way to remove red algae from a saltwater tank is to use a stainless steel scraper and manually scrape it off. To reduce red algae from growing, use less light in the tank and make sure there is not excessive phosphates and nitrates in the water.
"Removing about two thirds of water, wiping down the inside of tank with sponge or cloth, and cleaning out waste such as leftover fish food once every 2 weeks, will help keep it free of bacteria which causes red algae.'
Red Algae should be removed the same way that you would green or brown algae, either scrub it off the tank and the decorations or get a fish that eats the algae.
To remove red algae from your tank, you do need to maintain the tank on a regularly. Give it a good scrubbing,keep the substrate clean, regularly clean filtering system .
If you go to the local fish store they have a substance you spoon into your tank once a day. I believe its actually called red algae remover. It takes awhile for the algae to go away but it does work.