"API pH Down adjuster lowers pH to make freshwater aquariums more acidic for fish & plants when levels rise too high. pH is the measure of acidic or alkaline conditions in water, where a value of 7.0 corresponds to a neutral pH, pH values about 7.0 are considered alkaline, and pH values below 7.0 are considered acidic.
Determine the pH of aquarium water with an API pH TEST KIT. To lower pH, add 1 ml. for each 10 gallons of aquarium water. Take another pH reading before adding another dose of pH DOWN pH adjuster."