pH control products allow us to raise or lower the pH value of our nutrient so we are operating in the best range for our type of grow media, typically 5.5 - 6.3 for hydroponics and 6.2 - 7.0 for soil. These products are often concentrated acids, so many are available in store only and cannot be shipped. Customers should be extra careful handlings these items safely. We recommend powdered pH up and down for new growers because it's safer to use. Always adjust the pH of your solution after adding all your nutrients and additives.