TNB Naturals granular pH DOWN is non-caustic so it won't burn your hands and since it's so gentle, it won't harm the beneficial bacteria. It's even safe for use with aquaponics. TNB pH DOWN is composed of all natural ingredients with the addition of no harmful chemicals. This innovative way to lower the pH levels of your hydroponic or liquid fertilizer is both simple and cost effective. Simply add a small amount to your water, mix thoroughly and check your pH levels.