API pH Up

"API pH UP raises pH levels in your aquarium to make water more alkaline when 
levels fall too low. 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."

Recommendations

"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. Some fish may be sensitive to 
pH adjustments greater than 0.2 in a 24 hour period, so changes of this 
magnitude should be done with extreme care."