I have been advised to use hydrogen peroxide to dissolve some black metal stains in my fibreglass pool especially the vertical walls as these are difficult to clean with granular cleaning materials. I have solar heating pipes, and also a brand new aqua swim sand filter from speck. I have received conflicting advice as to how long I must leave it, whether it degrades to a harmless material, whether the pool should be circulating and how long it takes to degrade so that can one use it again, and whether it damages the sand or indeed sand filter and associated parts or the solar heating pipes. Some clarity would be most welcome, thank you