Here are my stats:
Total Hardness: very low (never raised it because its a vinyl pool)
I have shocked, filtered 24/7, (cleaned filters constantly),vacuumed, scrubbed and the green algae just keeps coming back.
Haven't used the poly algae killer stuff yet as I try to keep my chem usage as little as possible and not
sure this stuff works that well anyway, but it may be the only thing left I can try?