Dear friend ,
whatis suggested in the earlier reply is right. Check all parameters. esp. pH ( 7.2 - 7.4) and Total alkal;inity ( 200 - 300 ppm). If they r Ok.. then 'shock ' your pool by increasing Cl- level to 10 pppm for one day.
Algae will vanish.
remove dead algaae physically then run filter for 12 hrs. and then open the pool for use.
Ucan'yt go wrong.