Last year, I had an issue maintaining Free Chlorine. My Pool Guy said, I should just empty the pool and add fresh water. I opened the pool yesterday only to find a layer of green algae covering the bottom. Also, Zero FC. I added 2 lbs of Clorax Pool Shock. Water is still green and now cloudy. I am in the process of cleaning out all dead algae. As per my last test the Chlorine level was 1.0 and PH 7.5. Does anyone have any suggestions what I should do next to get the water crystal clear again?