Fresh Trace - 500 ml The 500 ml bottle of Seachem Fresh Trace is a top of the line nutrient additive that provides a wide range of essential trace elements that are necessary for optimal health and growth in freshwater fish. For greater efficacy, the solution is made only with ingredients that have been scientifically proven to contribute to improved development and overall health. Unlike terrestrial animals, fish obtain the nutrients they need to survive from both their food and their environment, making it absolutely critical that the proper water parameters are maintained without drastic fluctuations. And due to the fact that these essential trace elements are most often depleted in the aquarium through utilization, oxidation and precipitation, it is vital to restore them on a regular basis. Directions: Use 1 capful (5 mL) for every 80 L (20 US gallons) of aquarium water twice a week.