I tested my water for nitrates because of problems i had last season. I drained it several times about 2' below the skimmer. I dropped the level to 30 ppm before algae attacked when i went out of town on Labor Day. I closed the pool for the season and now I'm ready to open and I checked my water to find it measured 60 ppm on nitrates. Should I refresh my pool before balancing to achieve 25 ppm on the nitrates or just shock my pool and maintain FC. Will it take more bleach to achieve FC with the high nitrates or dose it matter?