Without proper fertilization, aquarium plants gradually yellow, drop their leaves and die. Aquarium plants require essential nutrients for vibrant growth. API ROOT TABS are formulated to supply key nutrients, including iron and potassium and carbon, to help new aquatic plants get off to a vigorous start and to keep established plants flourishing. These nutrients are consumed over time in the aquarium and must be replenished for plants to thrive. Safe for use with tropical fish.