Growth Technology PH UP or DOWN - pH adjustment concentrate - Growth Technology pH control is essential in a hydroponic system Plants in hydroponic systems function best with a nutrient solution pH of between 5.8 up to 6.5. Bottled in black and red – the internationally accepted packaging colours for aggressive liquids. Full compliance with all health and safety regulations. pH UP contains potassium hydroxide (KOH). This is a very caustic liquid and should be handled with extreme care. Once again our product, at 25%, is stronger than some competing products. Always check the label for best value.