Hanna Marine Calcium Checker HC – HI758

The Hanna Marine Calcium Checker HC – HI758 is a digital calcium tester designed specifically for saltwater and reef aquariums, giving you a clear calcium reading in ppm without having to judge subtle colour changes by eye.

For reef keepers who regularly monitor calcium and want more confidence in their testing, the HI758 provides a simple digital method with a measurement range of 200–600 ppm calcium and a resolution of 1 ppm. It is particularly useful for aquariums containing LPS, SPS and other calcifying organisms where calcium consumption needs to be monitored alongside alkalinity and magnesium.

Key Features

• Digital calcium testing for marine and reef aquariums

• Measures calcium from 200–600 ppm

• 1 ppm resolution

• Accuracy of ±6 ppm ±5% of reading at 25°C

• Large, easy-to-read digital display

• Removes the need to visually interpret a colour-change endpoint

• Simple one-button operation

• Automatic shut-off to preserve battery life

• Supplied with reagents for 25 tests

• Replacement HI758-26 Calcium Reagents available separately

• Compact protective storage case included

• Ideal for regular reef aquarium testing and dosing management

Why Test Calcium?

Calcium is one of the key parameters to monitor in a reef aquarium. Stony corals, coralline algae and other calcifying marine organisms continually use calcium as they build their skeletons and structures.

As a reef aquarium grows, its calcium demand can change considerably. Regular testing allows you to see how quickly calcium is being consumed and adjust supplementation, two-part dosing, Balling methods or calcium reactor settings accordingly.

Testing calcium alongside alkalinity and magnesium provides a much clearer picture of your reef aquarium's overall mineral balance.

Digital Results Without Colour Guesswork

Traditional calcium test kits generally rely on watching for a colour change and deciding when the test has reached its endpoint.

The HI758 instead uses a handheld colorimeter to measure the reaction and displays the result directly in ppm calcium on its LCD screen.

This makes it particularly useful for reef keepers who prefer a repeatable testing process without having to compare colours manually.

Important Testing Information

The HI758 uses a very small marine water sample and requires calcium-free deionised or suitable distilled water during the testing procedure.

Because the test is sensitive to very small amounts of calcium contamination, Hanna recommends taking care to keep the cuvettes and testing equipment clean. Residual calcium from tap water or unsuitable purified water can affect the result.

For consistent results:

• Follow the supplied HI758 testing procedure carefully

• Use clean cuvettes and testing equipment

• Avoid rinsing the test cuvette with tap water before testing

• Use suitable calcium-free deionised or distilled water

• Keep fingerprints, salt and water droplets off the outside of the cuvette

• Measure liquids accurately using the supplied syringes and pipette

What's Included

The Hanna HI758 is supplied as a complete testing kit with:

• Hanna HI758 Marine Calcium Checker HC

• 2 sample cuvettes with caps

• HI758 Marine Calcium starter reagents for 25 tests

• 1ml syringe with tip

• Minipipette with tip

• Plastic pipette

• 1 x AAA battery

• Protective storage case with custom insert

• Instruction manual

Specifications

Parameter: Calcium
Application: Saltwater and marine aquariums
Measurement Range: 200–600 ppm Ca²⁺
Resolution: 1 ppm
Accuracy: ±6 ppm ±5% of reading at 25°C
Light Source: LED at 610nm
Light Detector: Silicon photocell
Test Method: Adaptation of the Zincon Method
Battery: 1 x AAA alkaline battery
Dimensions: 86 x 61 x 37.5mm
Weight: 64g

Replacement Reagents

Once the included reagents have been used, the Checker can be refilled using:

Hanna HI758-26 Marine Calcium Reagents – 25 Tests

The Checker itself does not need to be replaced each time the reagents run out.

Perfect For

• Reef aquariums

• Marine aquariums

• SPS and LPS coral systems

• Monitoring calcium consumption

• Aquariums using calcium supplementation

• Two-part and Balling dosing systems

• Calcium reactor users

• Reef keepers wanting a digital alternative to traditional colour-change calcium tests

• New Zealand marine aquarium keepers wanting reliable ongoing calcium monitoring