Sounds to me like you killed the algae because it all settled to the bottom, making your water clear. But when you turned on the pump, and circulated the water, it stirred it off the bottom, and made everything cloudy again.

Only cure for this is to run the filter 24/7 until it filters all the dead algae out. It took mine about 3 days running 24/7.

You can floc, and shock and clarify all day long -- but filtering and time is what you need.