My water went green twice before I quit scrubbing the liner and fixed the real issue
Spent two weekends scrubbing algae off the liner in my 500 gallon pond before a guy at the pond store in Mesa asked how many hours of direct sun it gets, and it turns out 9 hours was my whole problem. Moved a shade sail over it two weeks ago and the water cleared up on its own, so how much sun are you all giving your ponds before fighting the algae?