I left my pool cover on for 3 days & opened it to a green mess on July 28th. When first tested phosphate was 1,710ppb ( I have a 15,000 gallon in ground pool). It was recommended to use a phosphate remover..wait 3 days, backwash, rinse & add 6 bags of shock, brush walls & floors. It got slightly better, where we could see low end of pool. Then it continued to get worse. While phosphate levels are at 208 now ( as of 08/26 ) & per store testing all other levels are within range (except CAcid has been above 140 since the start of this)..the last step taken was 4 bags of shock at night & Terminator Algaecide in the morning. This is 36 hours later...and nothing. I am starting to panic, because our season almost over & we will need to close. Everything I read says not to close a green pool. .I would just drain the pool by 70%...but that seems a poor idea at the end of the season. HELP My parents had this house /pool for 40 years and this never happened...I have been in charge since 2018....first incident. Please note we did have sand filter repaired & new "glass" sand added. Thank you in advance. Total Chlorine level is 18.12ppm ( free chlorine same)