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.