IODI+ and STRONI+ NANO combines 2 essential elements in 1-pack; Iodine is an essential element and is vital for coral development in closed reef tank environments. However, it is rapidly consumed by invertebrates and eliminated by the skimmer, the active carbon, the filter and coralline algae. IODI+ supplies the hard corals in your aquarium with the iodine they need to grow and for coloration. It also helps them to adapt to lighting variations and neutralizes the excess oxygen produced by Zooxanthellae under excessive lighting and therefore combats coral bleaching. IODI+ is also particularly recommended for Xenia, Anthelia, Clavularia, and corallimorphs. Strontium is an essential trace element in reef aquariums and is vital for coral development in closed reef tank environments. Strontium also stimulates the growth of hard corals and assists in the development of the red and coralline algae that produce the live rock decor. These organisms fix strontium in their skeletons along with calcium, which means that the strontium is in constant demand in aquarium environments. Trace elements are constantly replenished in the natural ocean environment but the strontium concentration quickly drops in a reef aquarium, meaning that it needs to be offset. STRONTI+ provides all the strontium needed for optimum and healthy coral, clam and coralline algae growth. The strontium diminishes proportionally with the calcium in a reef aquarium, so you can gauge the strontium demand by examining the calcium content.