My Husband and I are attempting to open a pool that was not closed during last winter. The pool is above ground 15,000 gal vinyl that was full of leaves, tree limbs and of course algae. When we had gotten all the leaves out of the pool that we could see, we changed the sand and took a sample to the local pool store. The process was alk up, ph down and shock. I did all of this and took a sample back again. The algae is in full force and they suggested that we floc the pool leave it set over night with the filter off and all would sink to the bottom to be vacuumed to waste in 24 hours. 24 hours later we have a huge amount of whitish green algae on the top of the water...now what? Help please!