Most hobbyist never think about supplementing things beyond the basic skeletal ions of calcium and alkalinity and the occasional magnesium. Granted Iron (Ferrous, aka Fe) isn’t mandatory for keeping many of our marine animals, it is however important for coloration and pigment creation in stony corals. It is also extremely important in applications where refugiums and mass macroalgae is being cultivated.
ReefGrow Ferrous Iron Pro provides an organic compounded iron which is readily available to both corals as well as macroalgae. Macroalgae will quickly strip valuable iron from a reef system and once depleted will begin to turn from a dark green to yellow. So for longevity of macroalgae iron is extremely important. Maintaining proper iron levels will increase the speed at which macroalgae grows, thus helping to transport nutrients from the reef aquarium for better usage by your macroalgae. It also decreases the likelihood of Caulerpa sp. undergoing sexual repoduction and causing explosions of nutrients in the water column.
Iron also is used in photosynthesizing organisms (coral included) in the breakdown of CO2 into C6H12O6 (which is a simple sugar aka glucose).