*	Handheld digital colorimeter designed to measure low range nitrate levels in saltwater aquariums
*	Accurately measure nitrate levels from 0 to 5 ppm (as NO3–) or 5 to 50 ppm (calculated) using dilution
*	Built-in timer and digital readout helps ensure accurate test results by eliminating common user errors

Upgrade from chemical test kits to professional instrumentation without breaking your budget. The Hanna Saltwater Nitrate Low Range Checker HC (Model HI781) is a sensibly-priced single parameter electronic tester for measuring low range nitrate levels in marine aquariums. This compact handheld colorimeter delivers the accuracy of professional instrumentation at the affordable price.

Easier and more accurate than chemical test kits the Hanna Saltwater Nitrate Low Range Checker HC provides a simple, accurate and cost effective way to measure nitrate levels from 0 to 5 ppm (as NO3–) or 5 to 50 ppm (calculated) following the dilution method. Accurate routine measurement of nitrate levels is essential to ensure proper coral and ornamental invertebrate growth in marine reef aquariums.

Hanna Instruments Marine Calcium Checker HC measures just 2.4" x 1.5" x 3.4" high and features a range between 0.00 to 5.00 ppm (as NO3–) with a ±0.25 ppm ±2% accuracy at 25 °C (77 °F) or 0.0 to 50.0 ppm (calculated) using the dilution method with a ±2.5 ppm ± 5% accuracy.

The Hanna Saltwater Nitrate Low Range Checker HC (Model HI781) is delivered in a case with custom insert and is supplied with: Marine Nitrate Low Range reagent starter kit (reagents for 25 tests), Sample cuvette and cap (2 pcs.), Filter paper (25 pcs.), Filter holder (1 pc.), Mixing vial and cap (1 pc.), 5 mL syringe with tip (1 pc.), 10 mL syringe (1 pc.), 1 mL graduated syringe (1 pc.), Plastic refilling pipette (1 pc.), 16 gauge blunt needle (1 pc.), 1.5V AAA Alkaline battery (1 pc.), and Instruction manual.

Specifications
Range:
0.00 to 5.00 ppm (as NO3–)
0.0 to 50.0 ppm (calculated) using dilution
Resolution: 0.01 ppm
Accuracy:
@ 25°C/77°F ±0.25 ppm ±2% of reading
@ 25 °C (77 °F): ±2.5 ppm ± 5% of calculated reading using dilution
Light Source: LED @ 525 nm
Light Detector: Silicon Photocell
Method: Colorimetric Method
Battery Type: (1) 1.5V AAA
Auto-off: After ten minutes of non-use
Dimensions: 86.0 x 61.0 x 37.5 mm (3.4 x 2.4 x 1.5”)
Weight: 64 g (2.3 oz)

Frequently Asked Questions Regarding the Hanna Saltwater Nitrate Low Range Checker HC (Model HI781)

Q. What is nitrate?
A. Nitrate is a by-product of the Nitrogen cycle. The nitrogen cycle begins when organisms produce ammonia as a toxic waste byproduct. From there, beneficial bacteria in the aquarium use the ammonia and convert it to nitrite, a less harmful byproduct. The nitrite is ultimately converted to nitrate by further oxidation from bacteria.

Q. How does nitrate affect aquariums?
A. While nitrate is essential for the growth and reproduction of plants, high levels of nitrate can really harm your fish and inverts. Over time, nitrate will adversely impact cell development, resulting in weakened immune systems and reduced growth.

Q. What is a healthy range?
A. There is no set value at what to keep your nitrate levels at. The ideal range for nitrates depends on the type of coral you keep, your ideology behind husbandry, and other factors. Some fish and inverts can be particularly sensitive to raised levels. Generally, it is best to keep nitrates on the lower side, below 15ppm, for inverts and other sensitive marine species. Fish are able to tolerate higher levels.

Nitrate Guidelines for Saltwater Aquariums
Parameter	Reef Aquarium	Fish Only	Nature (Coral Reef*)
Nitrate (NO3-)	Low Values Preferred	< 30 ppm	Variable (Typically < 0.1 ppm)

*NOTE that values for natural coral reefs are based on typical surface ocean value and can change.

Q. How do you measure nitrate?
A. Nitrate cannot be detected directly, as it is invisible and odorless. Instead, you will need to use a chemical test kit or colorimeter to measure the level of nitrate in your system.

Q. Why are low range nitrate measurements in seawater difficult to measure colorimetrically?
A. It can be difficult to achieve the sensitivity needed to accurately measure low concentrations because of the many possible interferents. This is why many test kits have such light colors in the low ends of the range.

Q. What is the benefit to using the HI781?
A. Most test kits on the market rely on a color change that needs to be judged by eye. These are notoriously inaccurate, especially in the lower ranges because many factors can alter how a color is perceived. The amount and type of light in the environment as well as other colors close by, and even fatigue all can affect how you perceive color. The Hanna Marine Nitrate Checker HC - HI781 is more accurate than standard test kits because the instrument reads the color digitally, producing a precise number.

Q. What method does the HI781 use?
A. The HI781 uses an adaptation of the zinc reduction method. The reaction between nitrate and the reagents cause a pink/violet tint in the sample in this colorimetric method. Some nitrate tests on the market use a cadmium reduction method. Cadmium is a heavy metal and is considered hazardous waste. Cadmium can adversely affect environmental and human health and must be disposed of in accordance to state and federal laws. By using the zinc reduction method, users can be less concerned about how they dispose of their waste.

Q. What are possible sources of interference in this method?
A. Main sources of interference are nitrite and copper.

Q. What is the function of each of the three reagents in determining seawater nitrate (NO3-) values in the HI781? What specifically does each reagent do to help accurately determine nitrate in seawater?
A. Reagent HI781A-0 is a buffer, intended to raise the pH of the solution to the optimum point for reduction of nitrite to nitrate. HI781B-0 is a mix of powders that includes zinc, which is what actually reduces the nitrite to nitrate. HI781C-0 is what you could call the indicator, and simply reacts with the emerging nitrite to form a bright pink color.

Q. What is the significance in using the filter?
A. Most zinc-based methods currently on the market leave the zinc in the sample during the reaction. This results in a "bleaching" effect during color development. This leads to much lower color development and inaccurate results at low levels. The Hanna Saltwater Nitrate Low Range Checker HC HI781 filters the zinc out of the sample for better repeatability, accuracy, and sensitivity at low concentrations.