Urban Green Farms PH DOWN reduces aquarium and aquaponics pH in freshwater aquariums to desired levels. Safe for fish and plants. Determine the pH of aquarium water with an API pH TEST KIT. To lower pH, add 0.5 teaspoon for each 25 gallons of aquarium water. Take another pH reading. For example the AquaSprouts is a 40 litre tank. You would only use 0.2 of a teaspoon to quickly reduce pH. 
 
pH levels are important for the health of your fish and your plants. If your tank waters pH value rises above the ideal 7, it needs a fast-acting treatment to bring it back down to desirable levels.