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Hanna Instruments Nitrate Checker - Low Range Marine (HI781)

$49.95 $37.46Save: $12.49 (25%)

Item #: HN78100

In Stock

HI781 Marine Nitrate Checker HC Handheld Colorimeter - Hanna Instruments

The HI781 Nitrate Checker HC by Hanna Instruments is a simple and accurate handheld colorimeter that uses the Beer-Lambert principle to determine nitrate concentration. The HI781`s low range of 0.00 - 5.00 makes it ideal for measuring the low nitrate levels found in saltwater aquariums.

Why are Nitrate levels important?
Excess nitrates in a reef system can lead to an overgrowth of undesirable algae and dinoflagellates. Alternatively, not enough nitrates can lead to starvation for SPS and other corals.

  • Designed to accurately determine nitrate levels in aquariums and marine biology applications
  • Low range is ideal for saltwater aquariums 
  • Easier to use and more accurate than chemical test kits
  • Dedicated to a single parameter
  • Simple one-button operation
  • Large LCD digital read out for added convenience
  • Auto shut-off to assure the battery wont be drained
  • Compact size for easy travel and storage


Range 0.00 to 5.00 pm (m/L) NO3
Resolution 0.01 pH
Accuracy @ 25°C/77°F ±0.25 ppm ±2% of reading
Light Source LED @525 nm
Light Detector Silicon photocell
Method Colorimetric method. The reaction between nitrate and the reagent causes a pink/violet tint in the sample.
Interferences Nitrite, copper
Auto-off After ten minutes of non-use
Environment 0 to 50°C (32 to 122°F); RH max 95% non-condensing
Battery Type (1x) 1.5V AAA Alkaline
Dimensions 3.4" x 2.4" x 1.5" (86mm x 61mm x 37.5mm)
Weight 2.3 oz (64g)
What`s Included:
  • (1x) HI781 Checker HC
  • (1x) Nitrate Reagent starter set (reagents for 25 tests)
  • (2x) Sample cuvettes with caps
  • (1x) Filter holder
  • (25x) Filter paper
  • (1x) 10 mL syringe*
  • (1x) 5 mL syringe with tip
  • (1x) 1 mL graduated syringe
  • (1x) Mixing vial with cap
  • (1x) Plastic refilling pipette
  • (1x) 16 gauge blunt needle
  • (1x) 1.5V AAA alkaline battery
  • (1x) Instruction manual
*Some HI781 Checkers were sent out containing a 12mL syringe instead of the 10mL. This will not affect the procedure or results. Please follow the directions outlined in the product manual and videos.

Additional Accessories (sold separately):

Manufacturer information

Hanna Instruments USA Aquarium Supplies
Hanna Instruments is a leading manufacturer of analytical aquarium instrumentation. They were founded in 1978 and are headquartered in Woonsocket, Rhode Island. When Hanna introduced pH Electronic Paper in 1986 it literally revolutionized the world of testing by allowing millions of people in various industries to test for pH in a simple, accurate and affordable way. Hanna employees are constantly challenging themselves to improve on existing technology and to invent new testing techniques with the common goal to simplify analytical testing. This applies not only to instrumentation, but also to sensors development, reagents and chemicals. Hanna also believes in controlling the quality of their products from inception to delivery so they manufacture everything themselves, from meters and electrodes to chemical reagents and buffer solutions.

4 Stars


Reviewed on
February 27, 2021

Yes, I would recommend this.

Makes life easier

Pros: Easy and accurate

Cons: Must follow directions

Using this testing system makes it much easier to get accurate readings on your Nitrates. No more guessing which color on a chart is the closest.

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Reviewed on
November 30, 2020

Yes, I would recommend this.

Great overall

Pros: Accurate

Cons: Complicated

A little complicated to use the first time but im sure its as simple as they couldve made it

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Reviewed on
November 12, 2020

Yes, I would recommend this.

Lots of steps, but more accurate than guessing colors

Pros: No guessing which color; precise measurement

Cons: Lots of steps

I hate testing my water but at the end of the testing there's always the guessing game, which color does it best match. This removes the guessing game and gives a much more precise number.

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Reviewed on
November 11, 2020

Yes, I would recommend this.

Hard to use

Pros: Accurate

Cons: Hard to use and requires a lot of preparation for the test

This tester is very nice but very hard to use and it takes about 20 minutes to get the results of your sample there’s other ones out there that are much easier to use however this one is very accurate with the results

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Reviewed on
November 02, 2020

Yes, I would recommend this.

Finally, no comparing colors!

Pros: Accurate and no fiddling or guessing as to what number matches the color.

Cons: It is a little more involved, but that’s the nature of chemistry.

Nitrate is probably one of the most involved tests out there. Just look at the redsea kit. I find the Hanna checker to be quicker and also helps take the guesswork out of determining what the final number is.

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Reviewed on
October 25, 2020

No, I would not recommend this.

Waste of Money

Pros: none

Cons: not accurate

I love my Hanna Checkers . I use them all the time. I saw their nitrate tester so I ordered it based on experience I have with the other checkers. I read instructions and watched videos on properly use but their checker seems to be an inaccurate piece of junk. My Salifert test kit reads nitrates at 2, my. ATI water test reads 2.7, and my API test reads 0. The Hanna checker reads my nitrates at 13.4. What's Marine Depots return policy for returning crappy products?

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Reviewed on
October 23, 2020

Yes, I would recommend this.

Good tester

It's probably the most complicated to use Hanna I own but worth the effort. It's about as difficult as the Calcium Hanna tester. It does seem accurate when comparing to my red sea results. I really do like not having to use a color wheel as this gives me an exact number.

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Reviewed on
October 15, 2020

No, I would not recommend this.

Not straight as other hanna tests

Pros: no color guessing

Cons: not simple as other hanna tests

I love hanna’s alkalinity and phosphate tests. Hanna nitrate uses two sachets and a paper filter. Not sure what I disliked more, the test or the cleaning. Overly complicated compared to red sea nitrate pro, you need to be absolutely color blind to justify all the hassle. Not sure if want to use this again, will keep it as back up.

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