With the Salifert Profi Test O² you can determine the oxygen content in freshwater oder seawater exactly and easily. Oxygen is highly essential for all life forms. Especially corals and marine fish require oxygen concentrations at saturation level. This is because of the low solubility of oxygen in saline water which is approx. 5 - 7 ppm. The oxygen test measures oxygen concentration in just a few minutes. The Salifert Profi Test PO4 -Phospahte- can perform approx. 50 measurements in freshwater, marine water or water from garden ponds.Do you have questions about this article ?