Adopt the Salifert Oxygen Profi-Test to keep your corals and fish healthy! Oxygen concentration is vital in saltwater, so regular, reliable testing is essential—and the Profi-Test is designed to deliver! It's lightning-fast, with results in only minutes, and reads between 2-14 mg/L. The kit includes all the reagents and supplies for 40 tests, so you're set for months. Plus, it works for all kinds of water—marine, fresh, and garden pond. Be sure to read the safety instructions before using and always keep it out of reach of children. Make sure your aquariums have at least 8mg/L of oxygen and marine water at least 7mg/L for healthy fish!