SWG is for Salt Water Generator. It converts salt into free chlorine so you don't have to manually add bleach. Is your FC too high? I doubt it, and since you need to do a "SLAM" I can almost guarantee it's not high enough. But to know how high your FC "should" be, we need to know your CYA (stabilizer) level. But you need to test that yourself with one of the recommended test kit (TF-100 or Taylor K-2006). Do not trust pool store testing. It's almost never reliable.
When you have algae and it goes from green to cloudy, the organics are still alive and in there. A simple shock from pool store powders won't do the trick. That's where the "SLAM" comes into play.