I recommend Cutrine plus either granuals or as a spray or both. It will definitely knock it down and the copper is chelated so that very little is released to the pond and fish. Use it before the Tilapia are added and you should get good control.
I agree with this. We use Cutrine and it works great. Be careful not to treat to much at one time. The act of killing vegetation causes oxygen to be used up so if you kill to much at once your fish can suffer or you might have a fish kill. Once you've done an initial cutrine treatment, I would stock tilapia. Stocking this early in the year gives them plenty of time to do what they need to before the summer where algae growth is through the roof. Plus they provide great forage to any predators in the lake (they spawn multiple times) so they have a double benefit and are much cheaper than chemicals. They do however die off in the winter months because they can't handle cold temperatures. Still cheaper than chemicals and an annual purchase rather than multiple times a year. If you want to talk to someone about chemical prices, application rates, or information about tilapia give us a call at Pond King Inc. We specialize in this kind of thing. (940) 668-2573