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Ultra Low Range Phosphorus Checker® and Related Products

  • Our ultra-low range phosphorus colorimeter brings you more precise technology from your typical chemical test kit.

    ·       Remove the human error from your testing

    ·       No need to count drop or titrate your sample

    ·       Detects color changes your eye cannot

    ·       No calibration required

    ·       Get east, quick and consistent results

    ·       Accurate and affordable

    ·       Cost efficient: Once you purchase the Checker, reagents are sold separately saving money long term

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    The HI736 Checker® HC (Handheld Colorimeter) is a cost-effective way to measure phosphorus (orthophosphate as phosphorus) in marine systems, including reef tanks. Testing for orthophosphates is standard practice for saltwater aquariums and provides valuable insight into your reef tank’s water chemistry to help ensure long-term coral health. Phosphorus is an important parameter to measure in aquaculture and aquariums; levels that are too high can lead to extensive algae growth and prevent coral calcification and growth. 

    Learn more about the Phosphorus & Phosphates in Your Reef Tank and get your Phosphorus to Phosphate Conversion Table

    Features at-a-glance:

    ·       Most popular phosphate meter for reef aquariums. 

    ·       To convert phosphorus ppb to phosphate ppm multiply the reading by 3.066 then divide by 1,000

    ·       Saltwater only, best for SPS dominant aquariums and low nutrient systems

    ·       Reads as low as 1ppb phosphorus or 0.003 ppm phosphate (reads in parts per billion phosphorus)

    ·       Reads as high as 200ppb phosphorus or 0.613ppm phosphate

    ·       Comes with 6 tests, reagent refill for 25 tests: HI736-25 



    0 to 200 ppb


    1 ppb

    Accuracy @ 25°C/77°F

    ±5 ppb ±5% of reading

    Light Source

    LED @ 525 nm

    Light Detector

    silicon photocell


    adaptation of the Standard Methods for the Examination of Water and Wastewater, 20th edition, Ascorbic-Acid method


    0 to 50°C (32 to 122°F); RH max 95% non-condensing

    Battery Type

    (1) 1.5V AAA


    after three minutes of non-use and two minutes after reading


    81.5mm x 61mm x 37.5mm (3.2" x 2.4" x 1.5”)


    64 g (2.25 oz.)

    Ordering Information

    HI736 Checker® is supplied with (2) sample cuvettes with caps, phosphorus ULR reagent starter kit for 6 tests (6 powder reagent packets), battery, instructions and quick start guide.


    1 year limited warranty