Discus Trace™ supplies a broad range of trace elements demonstrated* to be necessary for proper fish health and growth. Unlike terrestrial animals, fish obtain nutrients from both their food and environment. Trace elements are normally depleted by utilization, oxidation and precipitation, thus it is important to restore them on a regular basis. Discus Trace™ contains only those elements actually demonstrated* to be required by fish. Aquarium salt is often used to add salts back to aquarium water. Some fish will tolerate this therapeutic use of salt; however, some fish are less tolerant. Discus as a species will not tolerate this elevated level of sodium in the water. If you keep live plants in your discus aquarium, the plants will not tolerate this either. Discus Trace™ is a well rounded trace mineral supplement that does not contain sodium and is used to replenish trace and ultra trace minerals that are demonstrated to be necessary for fish health and growth. *Nutrient Requirements of Fish, National Academy of Sciences, pp. 16-21,1993. Use 1 capful (5 mL) for every 80 L (20 US gallons) twice a week