API pH Down 16oz.

Slowly lower the pH of your pond water to make it more acidic using API Pond pH DOWN. This product slowly neutralizes alkaline substances that cause high pH, which limits the ability of aquatic plants to absorb necessary nutrients. pH DOWN is safe for pond fish and aquatic plants, and contains no algae-promoting phosphates. 

API pH Up & pH Down Dosage
To Lower the pH Add 1 teaspoons per 50 gallons of pond water. Carefully mix desired dose with 2 gallons of pond water in a plastic bucket and distribute evenly around the perimeter of the pond.
To Raise the pH Add 2 teaspoons per 50 gallons of pond water. For best results, add to water flow.
pH should not be raised or lowered more than .5 units every 24 hours. Do not treat the pond more than once in a 24 hour period.
Repeat treatment as necessary.