Maintaining stability in your reef aquarium is the most important factor for your success. In order to maintain that stability, you need a reliable testing solution that is easy to use and provides accurate results.

Hanna Instruments checker colorimeters have really changed the game when it comes to testing critical parameters and the dKH Alkalinity Checker is at the top of our list. It's quick, easy to use, provides accurate results, and covers one of the most volatile and critical parameters reef tank owners need to manage. 

Hanna Instruments Alkalinity Checker Colorimeter Package
Hanna Instruments Alkalinity Checker Colorimeter Package Contents

The Alkalinity Checker includes everything you need to measure alkalinity and is designed specifically for seawater and saltwater aquariums. There is a necessary liquid reagent required for each test and you get enough reagent for up to 25 water tests right inside the box. Additional dKH reagent is sold separately and you can also buy a reference solution to verify your checker is measuring accurately which is recommended at least every 12-24 months. The checker is powered with a single AAA battery which is included and should be replaced as needed. When cared for properly, the checker itself should last years. 


  • Range: 0.0 to 20.0 dKH
  • Resolution: 0.1 dKH
  • Precision: ±0.3 dKH ±5% of reading
  • Light Source: LED @ 610 nm
  • Light Detector: Silicon photocell
  • Environment: 0 to 50°C (32 to 122°F); RH max 95% non-condensing
  • Battery Type: (1) 1.5V AAA
  • Auto-off: After 10 minutes of non-use and after read
  • Dimensions: 81.5 x 61 x 37.5 mm (3.2 x 2.4 x 1.5")
  • Weight: 64 g (2.25 oz.)
  • Method: Colorimetric method

What's Included:

  • HI772 Checker
  • 2x sample cuvettes with caps
  • 1 bottle of alkalinity reagent hi772-26
  • 1 ml syringe and tip ­­­
  • battery
  • instructions
  • quick start guide.

How To Use an Alkalinity Checker Colorimeter

Testing is incredibly simple and can be done in under 2 minutes. The device is a digital colorimeter meaning it measures the intensity of color in your sample water by shining light through the sample. The reagent itself creates a certain level of color intensity based on your water's alkalinity level. The most important thing for ensuring accurate results is keeping your cuvettes clean and free of any fingerprints or smudges. Keep a dry cloth with your checker to dry and wipe down the cuvettes during testing.

Sample vial
Add reagent
Get Results
  1. Fill the cuvette with 5 mL of aquarium water, secure the lid, and wipe the cuvette clean.
  2. Push the button to turn on the checker.
  3. When C1 displays, place the cuvette with water into the checker colorimeter and close the lid. 
  4. Press the button to reference the sample water.
  5. When C2 displays, remove the cuvette.
  6. Draw 1 mL of reagent into the syringe using the plastic tip.
  7. Add all of the reagent to the sample water, secure the lid, and invert the cuvette 5-10 times.*
  8. Wipe the cuvette clean and place the cuvette back into the checker, close the lid, and press the button
  9. Results will display on the checker within 30 seconds.**

*DO NOT SHAKE cuvette to avoid creating air bubbles
**Note the checker only displays results for a short time before it automatically turns off, don't forget to look at the measurement before it turns off.