Dymax Iron Supplements are made of activated bio-ferric tablet that provides stable and long lasting nutrients that do not easily oxidize in water compared to any other ordinary iron nutrient. It also contains various essential “Trace Elements” which helps to enhance all natural colours of a plant without effecting fish. Directions: Add each tablet for 20L of water. Repeat the application weekly. In order to prevent quick oxidation of iron insert the iron supplement tab 1cm below the gravel surface. 50 tablets per box.