I found out by reading on this site that CYA being to high can cause algae growth. I'd never heard of cya before this. My pool is cloudy green for the third time in the last two months, I've been "pool stored" beyond belief and need help. I just bought a test kit at Walmart that will do a cya test and my level was 100. I understand a drain and refill is the only way to correct this, but how much do I need to drain? 50%?