If Tilapia aren't legal to be stocked in NY, or they are legal and the OP doesn't stock them, then the algae will need to be treated bi-weekly. It grows back that fast.
Bi-weekly treatments from a professional applicator sounds prohibitively expensive!
I am now 0 for 2 on helpful advice.
Fortunately, I am just stupid enough to take a third bite at the apple.
The algae grows on many of the same nutrients in the water that other aquatic plants also utilize. Perhaps you could read some of the threads on beneficial aquatic plants?
Some shallow water emergent plants that add to the look of your pond would "steal" some nutrients from the algae. Likewise, some submerged plantings of aquatic plants could also help if you like that look.
You could even do some things like water lilies in submerged plastic pots so you can control their spread.
Good luck on returning your pond to an attractive state!
