James you have used Reward which is a contact herbicide. This provideds a burndown but does not kill the root. I would use a algae control like Cutrine to work on your algae mats after the plants die. If you want to get rid of the milfoil you will need to use systemic herbicide like Sonar or Avast in the spring. You can also use a few other herbicides that go after the root so you may not have any regrowth. Next spring get on the milfoil in late April to Early May so you don't have so much dead biomass when treated.