#1 DO NOT DRAIN THE WATER OUT!! unless you plan on having the pool collasping or you are planning to replace the liner. #2 just shock, shock, and shock. keep your cl level high for a few days and it will die out and slowly clear up. make sure you brush it several times a day so the shock can hit the algae. and do not use soap as it is very hard to get out and will foam up your pool. patience will do it.