Wasn't sure if this was somewhere in the forum, tried finding it to no avail.

A little bit of info on what each fert. does for your water/plants.

Potassium - Protein synthesis, water and charge balance, enzyme activation.
Boron - Chlorophyll production, flowering, root growth, cell function.
Carbon - Required for all organic compounds.
Calcium - Cell wall stability and permeability, enzyme activation, cell response to stimuli.
Chlorine - Water and charge balance, photosynthesis.
Copper - Component of enzymes utilized in redox reactions that take place during photosynthesis.
Iron - Required for photosynthesis, component of enzymes utilized in redox reactions.
Magnesium - Component of chlorophyll, enzyme activation.
Manganese - Formation of amino acids, enzyme activation.
Molybdenum and Cobalt - Required for nitrate reduction.
Nickel - Enzyme activation, processing of nitrogenous material.
Sulfur - Component of proteins and the co-enzymes that are involved with nutrient utilization and growth.
Zinc - Chlorophyll production, enzyme activation.

Note that Oxygen and Hydrogen are also required, but are available at all times through water.