Hanna Checker Marine Alkalinity (HI755)
Hanna Instruments
A palm-sized digital colorimeter that reads alkalinity as a number instead of a color guess: fill the cuvette, add reagent, and the HI755 reports 0–300 ppm with 1 ppm resolution for about $50.
Why it mattered
Before the Checker line, a keeper chose between titration kits judged by eye against a fading color chart and laboratory photometers costing hundreds of dollars. Hanna, founded in Italy in 1978, had the photometer expertise; the Checker HC line, launched in 2010, shrank it into a $50 egg-shaped device.
The marine alkalinity Checker opened for pre-orders in September 2010 at $49.50, with reagents at about $9 for 25 tests. Alkalinity was the right first target — the parameter reef keepers test most, and the one where a number beats a shade of blue-green.
The HI755 made digital testing a routine rather than a luxury, and the Checker family spread across phosphate, calcium, nitrate, and more. Consistent numbers, logged over time, quietly changed reef keeping from reacting to crashes to watching trends.
Key specs
- Range 0–300 ppm (mg/L) alkalinity, 1 ppm resolution
- Accuracy about ±5 ppm ±5% of reading
- LED light source at 610 nm with silicon photocell detector
- Launch price $49.50; reagents about $9 per 25 tests
- Runs on a single AAA battery; auto-off after 10 minutes
Keeper notes
- Keepers swear by technique: a clean, fingerprint-free cuvette indexed the same way every test keeps readings repeatable.
- Reagent handling matters — incomplete mixing caused early accuracy complaints that Hanna answered with longer recommended mixing times.
- Many keepers cross-check a new reagent batch against a known standard before trusting a shift in readings.