Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants how much chemical should I apply

Treat with the prescribed dosage for the infested area only, based on the estimated acre-feet of water within the infested areas.
Your question is a valid issue. In some cases, dosage-rates can be challenging - especially since the smaller the area being treated, the greater the likelihood for premature product dispersion; which presents a question of how to allow for or offset the rapid dispersion of product from the treatment area.
Overall, treatment technique may be just as important as the product's dosage. Thorough penetration of floating algae mats is very important, since topical "raindrop" applications may only provide marginal success.