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HI-772 Seawater/Marine Alkalinity (dKH) Colorimeter - Checker®HC

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The HI-772 Alkalinity Checker is designed specifically for use within saltwater and coral reef aquariums, measuring directly in dKH (degrees of calcium hardness) with no need to convert readings from ppm. This digital alkalinity tester enables you to accurately measure the calcium hardness within your marine fish tank to determine if you are in the best dKH range for your saltwater aquarium requirements. Stability in dKH is key for healthy coral growth and precipitation, helping to maintain a steady pH for a healthier tank.

Hanna Checkers are convenient, easy and fast to use, with a single-button operation and a user-friendly handheld design for the precise measurement of marine alkalinity and other key fish tank parameters.

Accuracy ±0.3 dKH ±5% of reading

£72.00 (exc.VAT)
£86.40 (tax incl.)
Full Description Specification Manuals

HI-772 Marine Alkalinity Checker

The HI-772 Checker is an accurate electronic tester for measuring alkalinity in saltwater and coral reef aquariums. This practical, palm-sized digital tester requires a 10 ml water sample from your tank to precisely determine the dKH - degrees of calcium hardness - within your aquarium water. Single-button operation and four steps to test makes the HI-772 an effortless option for quick alkalinity testing.

This electronic dKH tester covers a comprehensive range of testing for marine aquariums, from  0.0 to 20.0 dKH. A single AAA battery is included with your starter kit for immediate use. An in-built auto-power-off feature saves battery life for fast measurement every time you need to test.

Why measure marine alkalinity?

Alkalinity is a key parameter for saltwater aquariums as it helps to maintain a stable pH, which is vital for most forms of aquatic life. Corals require an adequate dKH level to support healthy growth, with fluctuations or low levels resulting in impaired growth and precipitation. Regular monitoring of alkalinity allows for quick correction of changes in alkalinity for the health of your marine tank.

Using an accurate digital Checker to measure alkalinity in reef and saltwater tanks provides immediate insight into the condition of your water. Prompt, precise information allows you to make changes quickly, preserving the condition of your corals and providing fish with the optimal parameters necessary to thrive.

How does the HI-772 work?

The HI-772 Checker uses a colourimetric method. In this method, the reagents that are provided with the Checker are introduced to the sample vial to create a measurable reaction. The reaction between the water and reagents causes a yellow to blue to green tint in the sample, which is then read by the Checker, providing a digital readout of the level of alkalinity.

The HI-772 includes a reagents starter kit with reagent for 25 tests, for testing alkalinity straight out of the box.

Four steps to test

Step 1  1. ‘Zero’ the Checker with your vial & 10 ml water sample inside

Step 2  2. Take your vial out and add your reagent

Step 3  3. Place your vial into your Checker

Step 4  4. Press the button and read the results

Checkers vs test strips

Many saltwater and coral reef fish tank owners choose alkalinity test strips to measure the dKH in their water. However, test strips rely on personal perception of results, using a colour chart to determine the results of the reaction. Checkers offer a practical, electronic way to measure alkalinity, with digital results displayed on the screen and no guesswork involved.

Where can the HI-772 Alkalinity Checker be used?

The HI-772 is specifically designed for use in saltwater and reef aquariums, providing accurate results in dKH.


  • Simple, compact design
  • Accurate to ±0.3 dKH ±5% of reading
  • Dedicated to a single parameter
  • Includes AAA battery for operation
  • Powers off after 10 inactive minutes
  • Built-in timer for timed reaction readings

Order Information:

The HI-772 Checker is supplied with 2 cuvettes and caps, a seawater alkalinity reagent starter kit x 25 tests (HI-772-25), a syringe with a tip, 1 x 1.5V AAA battery, and an instruction manual.

Order more reagents with code HI-772-25 for the HI-772 Marine Alkalinity Checker.

Safety Data Sheets

When using any form of chemical, such as Hanna reagents, it is important you download the relevant safety data sheet and make yourself aware of any precautions you should take when handling the chemical. You can access our library of safety data sheets and download a copy by following the link below.

Please note that the '-' in HI- products should be removed from all searches to find the correct information.


Read More

Range0.0 to 20.0 dKH
Resolution0.1 dKH
Accuracy±0.3 dKH ±5% of reading
Light SourceLED @ 610 nm
Methodcolorimetric method
Environment0 to 50°C; RH max 95% non-condensing
Battery Type(1) 1.5V AAA
Auto-offafter ten minutes of non-use
Dimensions86 x 61 x 37.5 mm
MethodColorimetric method. The reaction causes a distinctive range of colours from yellow to green to blue to develop

Ordering information: HI-772 is supplied with sample cuvettes with caps (2), seawater alkalinity reagent starter kit (reagents for 25 tests), syringe with tip, battery, instructions and quick start guide.