In aquaponic systems, sulfur is rarely deficient. It’s one of the reasons you hear about it so often. In fact, sulfur is more often present in larger-than-necessary quantities, primarily because we love to use supplements that are sulfate based.
Sulfur is another secondary macronutrient (along with calcium and magnesium). It occurs in aquaponic systems as sulfate (SO4²-), a soluble anion. Sulfate is taken up directly by the plant and is very important in the production of many amino acids, proteins, and oils.
In many crops, sulfur is as important as phosphorus to plant growth and development! Without enough sulfate, plants will be spindly, with yellowed new growth.