Hanna Instruments HI772 dKH Alkalinity Checker HC

Skip the color charts. The Hanna Instruments HI772 Marine Alkalinity (dKH) Checker HC is a pocket-size digital colorimeter that reads reef tank alkalinity from 0.0 to 20.0 dKH at 0.1 dKH resolution, using the same fixed-wavelength LED measurement principle as Hanna's benchtop photometers. Add reagent, press the button, read the number. Keep a fresh bottle of HI772-26 reagent on hand and browse the rest of our water testing kits.

Why Alkalinity Matters

Alkalinity (carbonate hardness) is the parameter reef keepers watch most closely. It buffers pH and is consumed around the clock as corals and coralline algae build skeleton, so it drifts faster than calcium or magnesium and swings are what stress SPS and LPS corals. Most reef tanks are held somewhere between roughly 7 and 11 dKH, and the key is stability. A digital reading you can trust, taken on a regular schedule, lets you tune your dosing before the corals show a problem.

Features

• Digital dKH readout: 0.0 to 20.0 dKH range, 0.1 dKH resolution and an accuracy of plus or minus 0.3 dKH plus or minus 5% of the reading.
• Photometer accuracy in your pocket: a fixed-wavelength 610 nm LED and silicon photocell detector replace subjective color matching.
• One-button operation: zero the meter with a plain sample, add the reagent, press and read.
• Liquid reagent: one 1 mL dose from the included syringe per test, 25 tests per HI772-26 bottle, no powder packets to fumble.
• Battery friendly: runs on a single AAA and shuts itself off after 10 minutes of non-use and after each reading.
• Compact: 3.2 x 2.4 x 1.5 in and 64 g, so it lives next to the tank and travels to frag swaps.

How to Test

1. Rinse a cuvette with tank water, fill it to the 10 mL line, cap it and wipe the glass clean of fingerprints.
2. Turn the Checker on, insert the cuvette and press the button to zero the meter on your plain sample.
3. Fit the tip on the syringe, draw HI772-26 reagent exactly to the 1 mL mark and add it to the same cuvette. Cap and invert gently to mix.
4. Insert the cuvette again and press the button. Your alkalinity appears on the display in dKH.

Test at room temperature and follow the timing in the included instructions. Use reagent from a bottle that is within its printed date for the best accuracy.

Specifications

What's Included

• HI772 Checker HC
• 2 sample cuvettes with caps
• 1 bottle of HI772-26 alkalinity reagent (25 tests)
• 1 mL syringe with tip
• 1.5 V AAA battery
• Instructions and quick start guide

Recommended Pairings

• Hanna HI772-26 dKH Alkalinity Checker Reagents, the 25-test refill bottle
• Hanna HI772-11 Calibration Check Set, to confirm your Checker is reading true
• Hanna HI713 Phosphate Low Range Checker, the next parameter most reef keepers add
• Hanna HI782 Marine Nitrate High Range Checker, for nutrient tracking
• Hanna HI764 Ultra Low Range Nitrite Checker, for new and cycling systems
• BRS Kalkwasser and Seachem Reef Kalkwasser, to replace the alkalinity your corals consume
• More water testing kits

FAQ

How is this different from a drop or titration test kit? There is no color matching and no drop counting. You add one measured dose of reagent and the Checker reads the color change electronically, so two people testing the same water get the same number.

Does it read ppm or meq/L? The HI772 reads in dKH. To convert, 1 dKH is about 17.9 ppm of calcium carbonate, or 0.357 meq/L. If you prefer ppm, Hanna's HI755 Marine Alkalinity Checker reads in that unit.

How many tests do I get? Each HI772-26 bottle gives 25 tests, and the reagent carries a printed expiration date. Replace it with a fresh bottle when it runs out or expires to keep readings accurate.

Can I use it on a freshwater tank? The HI772 is calibrated for marine water. For freshwater, use the Hanna HI775 Freshwater Alkalinity Checker.