I use Cutrine Plus LIquid in a customers 5/8 acre pond that has 10' max depth, shaped sort of like a rectangle with rounded corners. I will use 1/2 gallon at a time, mixed with 5 gallons of water and sprayed with a backpack sprayer around the edges of the pond to kill the FA before we stock Tilapia, and maybe once more in the year if needed.

There are a dozen Koi in the pond along with LMB and BG.

I've been doing this for about 8 years now with no ill effects to the Koi. I wouldn't try a stronger dose of Cutrine Plus though. Some Koi in this pond are approaching 20 years of age.