Kent Marine Essential Elements, 16oz. Kent Marine Essential Elements replaces biologically important trace minerals which are removed by marine fish and invertebrates, and removed through protein skimming, ozone, and especially carbon filtration. Designed for fish only and reef systems. Essential Elements is unmatched in its ability to increase vigor and color! Does not contain detrimental heavy metals, phosphates, nitrates, or silicates. Does not promote the growth of undesirable algae growth.