Do they work as they claim and are they necessary? I have had a problem chasing algae, and when I shock the water, the dead algae settles on the floor of the pool and I vacuum to waste to remove it. If I go through the filter, the water gets very cloudy and the stuff settles on the bottom again. Vacuuming the whole pool takes a long time and uses plenty of water, and have been told that if you add a flocculant, it helps I to clump together and settle, then you gently brush it to one area, let I settle again and vac it out. Does this actually work?