Salifert Oxygen Profi-Test Corals and marine fish require very high levels of oxygen concentration because of the low solubility of oxygen in salt water so it is very important to regularly test the level of oxygen present. The Salifert Oxygen Profi-Test is extremely fast, measuring oxygen levels in just a few minutes. Can be used for marine, fresh and garden pond waterWarning!Reagent O2-1 is irritating and contains a base. In case of contact with the skin wash with plenty of water. In case of contact with the eyes wash with plenty of water and consult a physician immediately. If swallowed contact a physician immediately.