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Clownfish in PlantsWhether you are maintaining your main reef tank or trying to give your frag tank the proper calcium dosage, using the digital readout from the Hanna Instruments Marine Checkers HC (Handheld Colorimeter) makes testing your tank levels so much easier. Keep reading to learn more about the full line.

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Video: Hanna Instruments Marine Line Colorimeters (2 minutes)


Checker Parameter Ideal Range Testing Frequency Why Test?

HI772 and HI755

Alkalinity in dKH (HI772) or ppm (HI755)

142-215 ppm or 8-12 dKH

Weekly to maintain, or as needed depending on your dosing schedule.

Vital for coral calcification and skeletal formation; prevents pH swings, alkalinity burn, coral bleaching, and tissue loss; improves equipment performance.


Nitrite (ppb)

Under 150 ppb – the lower, the better

First when setting up or cycling an aquarium, then as needed.

To make sure waste is being properly recycled.


Calcium (ppm)

Between 350-450 ppm

Weekly to maintain, plus every time you add or remove any organisms from your tank.

Vital for coral calcification and skeletal formation


Phosphorus (ppb)

More than 0 but less than 20 ppb

Weekly to maintain, or as needed if an excessive amount of algae growth is noticed.

High levels will prevent coral calcification or cause excessive algae growth 

Digital Readout, Accuracy & Repeatability

Hanna Instruments Marine Checker HC line provides quick and accurate results for alkalinity, calcium, nitrite, and phosphate/phosphorus in an easy-to-use digital readout. We designed the digital Checker HC to improve accuracy and repeatability over basic chemical test kits, which use color change as an indicator. 

Hanna Marine Alkalinity (dKH) Checker HC - HI772 and Alkalinity (ppm) Checker HC - HI755

HI772-b HI775-b

The Hanna Marine Alkalinity (dKH) Checker HC - HI772 and Alkalinity (ppm) Checker HC - HI755 provide a simple, accurate, and cost-effective way to measure alkalinity in parts per million (ppm) of calcium carbonate or as degrees Karbonathärte (dKH). Critical to the saltwater aquarium, alkalinity not only provides carbonate ions required for calcium carbonate skeletal regeneration of coral reefs, but it also acts as a buffer against large changes in pH.

Learn How to Use the HI772 and HI755 to check for Alkalinity (dKH or ppm)

Hanna Marine Calcium Checker HC - HI758


Accurately testing calcium levels is critical for everyone from coral reef hobbyists to aquaculture farms and research facilities. The Hanna Marine Calcium Checker HC HI758 is designed to make this process easier. The HI758 gives you a digital readout, not a color change, which takes out the guesswork and subjectivity.

Learn How to Use the HI758 Calcium Checker

Hanna Marine Nitrite Ultra Low Range (ULR) Checker HC - HI764


Nitrification is a multi-step process performed by nitrifying bacteria that converts ammonia to nitrate, with nitrite as a harmful intermediate product. Using the Hanna Marine Ultra Low Nitrite Checker HC - HI764 to check your aquarium's nitrite levels ensures a healthy environment for your fish, corals, and invertebrates.

Learn How to Use the HI764 Ultra Low Range Nitrite Checker

Hanna Marine Phosphorus Ultra Low Range (ULR) Checker HC - HI736

Hanna HI736-CheckerHC-Front

Phosphorus is one of the most important components for living organisms. However, many saltwater aquariums have high phosphates which can lead to excess algae and poor coral growth. The Hanna Marine Ultra Low Phosphorus Checker HC - HI764 allows you to measure and maintain phosphate levels at the ideal low quantities that are often challenging to test with traditional test kits. 

Learn How to Use the HI736 Ultra Low Range Phosphorus Checker

The Limits of Traditional Color-Change Test Kits

Many other test kits on the market rely on a color change that needs to be judged by sight. These are notoriously difficult to use, especially in the lower ranges. Hanna Instruments' Marine Checker line bridges the gap between simple chemical test kits and professional instrumentation. The one-button design makes testing easier and more accurate by outputting a consistent digital reading every time.

Don't Forget about Your Aquarium's pH Level!


The Hanna Checker Plus pH Tester HI98100 helps you accurately measure your saltwater aquarium's pH level to make sure it stays between the acceptable range of 7.9 and 8.5. When pH is not properly monitored, corals and other marine organisms can be at risk. pH levels in an aquarium that are too low or too high – or levels that fluctuate too often will put stress on marine life, which could cause them to die. Additionally, when pH levels drop too low it can prevent coral calcification from occuring.