u can take the rock out and try to take as much as u can off or
u can buy a lawnmower blenny to eat all that. thats there favorite food. see its in the name, they love grass type algae, there under water lawnmowers lol. but only one per tank.
Lowering your nitrates and phosphates should help, reduce light schedule. What type of water do you use for top-offs? A lawnmower may eat some but it is better to find and eliminate the cause of the algae, in order to stop it long term.