The Acid formulation uses food grade Phosphoric acid to lower the pH to the proper level.
To maximize plant growth, the pH level of your nutrients should be slightly acidic. Experienced growers consider the ideal pH for most crops to fall between 5.5 and 6.5. Users of General Hydroponics nutrient products generally do not experience problems maintaining the proper pH range because our formulas are pH buffered. However, some important exceptions do exist. pH can acidify to an unacceptable level when nutrient solutions are used with poor quality water, or pH unstable media, such as rockwool. High growth rates can also destabilize pH.