Kent Marine Essential Elements replaces bilogically 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 contacin detrimental heavy metals, phosphates, nitrates, or silicates. Does not promote undesirable algae growth.  8 oz treats 2400 gallons.