The tilapia rise to the surface of the tank as you tend the leafy green vegetables in your hydroponic garden. The combination of fish farming and hydroponics is called aquaponics. The nutrient rich water of the fish tanks is used as the hydroponic fertilizer, cycling through the system multiple times. While tilapia are tolerant of pH levels ranging from 5.0 to 10.0, your vegetables generally require a pH of 6.0 to 7.0 and sufficient macronutrients to thrive. To balance your system, you can add potassium to increase the pH and promote the growth and flowering of your fruits and vegetables.