Flourish is a comprehensive plant supplement for the natural freshwater aquarium. It contains a rich assortment of important micro elements, trace elements and other nutrients. These include calcium, magnesium, iron and other important elements that have been shown to be beneficial to aquatic plants. For macro element (NPK) fertilization, use Flourish Nitrogen, Flourish Phosphorus or Flourish Potassium as needed. Flourish is safe for invertebrates such as shrimp. Flourish is designed to be used in conjunction with other macro and micro-nutrient supplements. Other manufacturers try to include ALL necessary nutrients, leading to overdoses of micro-nutrients in an attempt to raise macro-nutrient levels. DirectionsUse 1 capful (5 mL) for each 250 L (60 US gallons) once or twice a week. For smaller doses, please note that each cap thread is approximately 1 mL. Refrigeration is recommended 3 months after opening.