A Cation is a metallic element with a positive charged ion that would be attracted to the cathode in electrolysis. A cation has more protons than electrons, consequently giving it a net positive charge. For a cation to form, one or more electrons must be lost, typically pulled away by atoms with a stronger affinity for them.
Cations as found in common spirulina culture medium formulas:
Sodium 4380 mg/l
Potassium 642 mg/l
Calcium 10 mg/l
Iron 0.8 mg/l