HI783 Hanna Checker HC Magnesium — Reef Colorimeter 1000 to 1800 ppm - Hanna

Hanna Checker HC HI783 pocket colorimeter for reef magnesium

The Hanna Checker HC HI783 is a pocket colorimeter dedicated to measuring magnesium in marine and reef aquariums. It bridges the gap between colour-comparison test kits (eye-balled readings, prone to error) and expensive lab photometers. A fixed-wavelength LED (466 nm) and a silicon photocell detector deliver lab-grade precision in a housing that fits in one hand.

In practical use, this Checker HC lets you hold reef magnesium between 1250 and 1350 ppm on an SPS or LPS tank. Matched reagent: HI783-25, 25 tests per bottle.

What this Checker brings to a reef keeper

• Digital readout down to 1 ppm — no more eye-balling colour cards.
• Method: Beer-Lambert colorimetric method — the same chemistry used by lab instruments.
• Accuracy ±25 ppm ±3 % of reading — solid enough to base dosing decisions on.
• Single-button operation (Zero + Read) — identical routine every measurement, fewer operator errors.
• Pocket-size 81.5 x 61 x 37.5 mm, 64 g — fits in a maintenance kit.
• Uses the dedicated Hanna reagent HI783-25 — controlled chemistry, repeatable readings.

Technical specifications

• Model: HI783
• Measurement range: 1000 to 1800 ppm
• Resolution: 1 ppm
• Accuracy: ±25 ppm ±3 % of reading
• Light source: LED at 466 nm
• Light detector: silicon photocell
• Method: Beer-Lambert colorimetric method
• Power: 1x AAA 1.5 V battery
• Auto-off: auto-off after 2 to 10 minutes depending on model
• Environment: 0 to 50 °C, RH max 95 % non-condensing
• Dimensions: 81.5 x 61 x 37.5 mm (3.2 x 2.4 x 1.5 in)
• Weight: 64 g (2.25 oz)
• Warranty: 2-year Hanna Instruments warranty

Measurement procedure

• Rinse the cuvette with RO water, then with sample water.
• Fill to the mark, insert the cuvette and press Zero.
• Add Hanna reagent HI783-25, agitate as per the datasheet.
• Reinsert the cuvette and press Read — the reading appears on the digital display.
• Rinse the cuvette immediately with distilled water to prevent residue.

Matched reagent and calibration set

• Hanna HI783-25 — magnesium reagents 25 tests — the reagent dedicated to this Checker HC; always use fresh reagents to preserve accuracy.
• Hanna HI783-11 calibration set — reference standards to verify instrument accuracy between measurement runs (sold separately).

Why get this Checker from ReefSolution

To build a complete reef testing station we also recommend:

• Hanna HI772 dKH alkalinity Checker — KH is the reef parameter that shifts fastest; measure twice a week.
• Hanna HI758 marine calcium Checker — completes the Ca/KH/Mg trinity.
• Hanna HI783 marine magnesium Checker — magnesium every 2-4 weeks.
• Hanna HI98319 waterproof salinity tester — for salinity in ppt/PSU/SG with temperature compensation.
• Hanna HI70024P 35 ppt calibration solution — the reference standard for validating salinity instruments.

Frequently asked questions

Which reagent works with the Hanna Checker HC HI783?

The matched reagent is Hanna HI783-25, sold in packs of 25 tests. Never use a reagent from another Checker model — the chemistry and the measurement LED are different.

How accurate is the HI783 on a reef aquarium?

Accuracy is ±25 ppm ±3 % of reading with a resolution of 1 ppm — plenty to drive a Ca/KH/Mg dosing routine or monitor a critical reef parameter. Always rinse the cuvette with distilled water and work at a stable temperature.

How do I calibrate or verify the HI783?

Use the Hanna HI783-11 calibration set (sold separately) — certified reference standards run periodically confirm the instrument is still within Hanna's tolerances.