Phosphorus Ultra-Low Range Checker - Colorimeter - Hanna Instruments

Phosphorus control is a fundamental part of managing a healthy reef system. Elevated phosphate levels fuel nuisance algae outbreaks, suppress coral coloration, and can suppress calcification in SPS corals. The Hanna HI736 Checker HC gives you a precise, repeatable phosphorus reading in a format that removes the guesswork inherent in colorimetric test kits that rely on the human eye to compare color swatches.

The HI736 operates as a dedicated single-parameter colorimeter, meaning it is purpose-built to read phosphorus in marine water at ultra-low concentrations. Where a standard test kit might give you a rough indication across a broad range, the HI736 resolves fine differences that matter when you are trying to hold phosphorus to a tight target — something SPS and mixed-reef keepers frequently need to do. The device accepts a prepared reagent sample and returns a digital result without any color interpretation on your part.

Usability is a clear design priority. The one-button interface walks you through the measurement sequence, and the portable handheld form factor means you can test at the tank rather than at a workstation. Reagent cuvettes load and read quickly, making routine testing less of a chore.

The HI736 is appropriate for reef aquariums, aquaculture systems, and general freshwater and marine water quality monitoring. It is best suited for hobbyists and professionals who have moved past basic test kits and want instrumentally derived numbers rather than visual approximations. Replacement reagent kits are required consumables and should be kept on hand alongside the unit.