Kent Marine Essential Elements replaces biologically important trace minerals which are removed by marine fish; invertebrates; through protein skimming; ozone; and especially carbon filtration. Essential Elements trace mineral supplement is designed for reef and fish-only Marine Aquariums. It is unmatched in its ability to increase vigor and color It does not contain detrimental heavy metals; phosphates; nitrates; or silicates. Essential Elements also does not promote undesirable algae growth. Size: 8 oz.