Aqueon Water Renewal helps to maintain the healthiest environment for your aquatic pets. Water in lakes and rivers contains renewable trace minerals that are essential for fish and plants to live and grow. In an aquarium environment, these minerals are depleted over time by fish, plants and carbon filtration. Aqueon Water Renewal replaces these biologically essential minerals, restoring water to its natural state and promoting the health, color, and vigor in fish. 4oz.