But those couple in the front... pull them out. They will spread even before you can get a handle on it receding. Also take some of the gravel that the runners are going through. I'm very laid back traditionally when it comes to nuisance algae. I have some byropsis right now in one of my tanks. It's been there forever. But yours really looks thick... some of the thickest I've seen, and looks oh so easy to remove the entire rock in th epic. If it's not so easy to remove, and that's just the look of the pic, we'll have to go at it another way.