How big is the pond and what is the average depth?
Fluridone takes some time to kick in, but if you are at the right PPB, you should start to see the watermeal leaves turning white. My experience with it is, you see whitening about 4 days into it and substantial whitening by 2 weeks. At this point it stops spreading. By 1 month it is pretty much pure white and by 2 months dies off.
With an infestation as bad as yours... You really need to watch for a fish kill not caused by the complete coverage but once the watermeal dies, all of it rotting in the pond will take up large amounts of DO.
