My previous post on my pressure problem got no replies but I think I answered my own question through research. Now that the heavy algae growth is dead and the water is nearly clear, I still have a filter pressure problem. I have to backflush many times a day to keep the pressure down. Is it possible that the slimy residue was so thick on the sand that a simple backwash will not remove it? I removed gross quantities of it from the skimmer and pump baskets but that is all gone now. Why is the pressure still building so fast?