My very first GW siege was cured by dosing with nitrate. It was pretty neat, dump 1 tsp of stump killer in the tank each day and every morning the tank was just a bit clearer. Alas, that hasn't worked since.
Now letting the floaters build up on the surface works great.
And since I have more biological media in the sump I [crossing fingers AND toes and knocking on wood] no GW for a while now even when I took everything out of the tank and did a major rescape in December.