I've used peroxide. I add water to a bowl then slowly add and mix peroxide till bubbles form on the algae. Then rinse and back in tank in high flow area. I'm sure there's a ratio of water to peroxide but I'm not sure what.
Same issue with mine but worse. Covered with gha. Did a peroxide 3% dip for 2 minutes. I didn’t dilute the peroxide just straight dip. Looks like it’s working. Zoas are still opening.