The HI736 Checker® HC (Handheld Colorimeter) provides a simple, accurate and cost-effective way to measure phosphorus in marine systems including reef tanks. Phosphorus is an important parameter to measure in aquaculture and aquariums; levels that are too high can lead to extensive algae growth, depleted dissolved oxygen levels, and ultimately can be fatal to many types of fish and aquatic life. Designed as a more accurate alternative to chemical test kits, the HI736 provides quick, accurate results in four easy steps: