Blister pack of the reagent refill for the nitrite NO2 test, two bottles visible, on a white background

The two reagent bottles numbered 1 and 2, the only contents of the refill

Reagent refill for NO2 nitrite test

Name: Reagent refill for NO2 nitrite test
Brand: Hardy Dewerse
SKU: J2412400
Price: 7.89 USD
Availability: InStock

$7.89

$2.63 × 3 with no fees Klarna.

This refill contains the two reagent bottles for the nitrite NO2 test, numbered 1 and 2, along with an illustrated instruction leaflet, for approximately 50 tests. The chemistry and number of tests are identical to those of the original kit.

Nitrite is the parameter tested most regularly — daily during the initial fill, then weekly thereafter. You reuse the glassware, sampling syringe, and colour chart from your nitrite test, all of which last for years.

Ref. J2412400·Reagent refill

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The summary

What the box contains: 2 reagent bottles numbered 1 and 2, and the illustrated instruction leaflet.
What it measures: nitrite NO2, the intermediate stage between ammonium and nitrate.
How many tests: approximately 50, the same as the original kit.
How often: one test per day for the first 3 weeks, then one per week.
Refill or complete kit: the chemistry is identical; only the accessories differ.
What gets sent to you: a parcel weighing 0.08 kg, bottles in their original packaging.

NO2 1 and NO2 2 reagents, approximately 50 tests, for aquarium, pond and aquaponics

This two-bottle refill lets you continue monitoring nitrite, which is the parameter most frequently tested in a live aquatic system. Written as NO2, it represents the intermediate stage of the nitrogen cycle: bacteria convert ammonium from fish waste into nitrite, which a second group of bacteria then converts into nitrate. Until that second group becomes established, nitrite accumulates and becomes toxic to your fish. Levels rise when a new tank is first filled, after a filter failure, or after filter media have been cleaned too thoroughly.

💧 How to read a measurement

Take 5 ml of water into each of the two test tubes. One receives 5 drops of each reagent, while the other is kept with untreated water to serve as a colour reference. After 5 minutes, the colour is fully developed and can be compared against the colour chart, with both tubes placed side by side in the grey comparator block. If your water is cold, leave the sample at room temperature for around 2 hours before testing, as the colour develops more slowly in cold conditions.

🌿 Nitrite in aquaponics

In aquaponics, your fish and plants share the same water, and the bacterial colony in the filter acts as the link between the two. Nitrite is the indicator of that colony's activity: as long as it remains measurable, part of the nitrogen has not yet reached the nitrate stage, the form your plants can take up. The recommended testing frequency is once a day for the first 3 weeks with a fresh body of water, then once a week thereafter. At that rate, the first period uses 21 tests, and the remaining 29 give you a further 29 weeks of weekly monitoring. The guide to the nitrogen cycle in aquaponics explains those first 3 weeks in detail.

A pale colour indicates degraded reagents

A paler colour than usual on water that has not changed points to degraded reagents, not cleaner water: the reading will come out too low, and a nitrite spike could go undetected. Reagent 1 also carries the Danger label, with H314 and H318, indicating severe skin burns and eye damage. Hold the bottle vertically with the tip pointing downwards, and keep the box out of reach of children.

Replace the individual bottles rather than the kit

Only the reagents are consumed, whereas the glassware, the syringe, the comparator block, and the colour chart from your nitrite test will last for years. Only replace the complete kit if the colour chart is stained or faded, or if a test tube is broken or scratched, as it is the chart that converts colour into a value. During cycling, the ammonium refill runs out at the same rate and is worth ordering at the same time.

The right time to order it is when you know consumption is about to pick up again, before the bottle runs out. Setting up a new tank, restarting a pond in spring, or receiving a new batch of fish each signal a period of daily testing. A gap in monitoring would otherwise fall at precisely the moment when levels can shift from one day to the next and become toxic to your fish.

📦 Contents and storage

You receive two reagent bottles with child-resistant caps, numbered 1 and 2, and an illustrated instruction sheet in French, for approximately 50 measurements. Screw the caps back on firmly and store the box in a dry place, in its original packaging and away from direct light. Keep the bottles at room temperature, between 20 and 25 °C, and never in the cold, as chilled reagents slow down colour development.

Technical specifications

What the refill contains

Contents: 2 reagent bottlesNO2 1 and NO2 2 reagents, numbered on the label, plus the illustrated multilingual instruction leaflet
Measurements: Approximately 50 testsThe same volume of reagent as in the original kit
Manufacturer's reference: JBL 2412400, PROAQUATEST rangeNot to be confused with reference 2412300, the complete test kit with all accessories.
Corresponding test: Nitrite NO2 test, ref. 2412300The refill is only compatible with the glassware, syringe, comparator block and colour chart supplied with this test

Testing frequency

Frequency at start-up: 1 reading per day for 3 weeksOn a new freshwater tank. Once a week on a new marine tank.
Frequency during maintenance: 1 reading per weekPlus one additional measurement after any illness or loss of fish.
Dose per test: 5 drops of each reagentOn 5 ml of water, in one of the two test tubes only, the other serving as a colour reference
Duration of a measurement: Approximately 7 minutesSix steps, including a 5-minute wait before the colour is fully developed

Security and dispatch

Hazard classification: Danger, reagent 1H314 and H318 on reagent 1, H226 and H319 on reagent 2. Child-resistant caps
Parcel weight: 0.08 kgOriginal blister pack, dispatched as is. Store dry at room temperature, in its packaging

To budget for separately

Both test tubes: Those from the nitrite testOne holds the treated sample, the other serves as a colour reference: you need two, not one.
Comparator block and colour chart: Those from the nitrite testThe grey block holds both tubes side by side in front of the colour chart — the only way to read the shade accurately.

4 further specifications are available in the detailed view.

In the box

2 reagent bottles with child-resistant caps, numbered 1 and 2
1 illustrated multilingual instruction leaflet, French included

Reference, EAN code, reagents-only note, number of measurements, dosages and measurement frequencies recorded from the JBL French-language data sheet and instruction leaflet on 07/10/2026.

Reorder the reagents, or reorder the test kit?

Both kits contain the same chemistry and give the same number of tests. What separates them is the accessories , and therefore what you already own.

Two bottles alone are not enough for a measurement Reading nitrite requires the grey comparator block, the nine-field colour chart, and both glass test tubes. Refilling requires all three parts to be in good condition.

	Reagent bottles (bottles)	Possible readings (measurements)	Illustrated instructions	Screw-top glass test tubes	Sampling syringe	Grey comparator block	Nine-field colour reading chart	Price
Recommended Reagent refill for NO2 nitrite testYour choice	2 bottles	50 measurements	Yes	No	No	No	No	$7.89
Nitrite NO2 water test in dropsYour choice	2 bottles	50 measurements	Yes	Yes	Yes	Yes	Yes	$15.90

Reagent refill for NO2 nitrite testRecommended

What gets used up

Reagent bottles (bottles)2 bottles

Possible readings (measurements)50 measurements

Illustrated instructionsYes

What lasts for years

Screw-top glass test tubesNo

Sampling syringeNo

Grey comparator blockNo

Nine-field colour reading chartNo

Budget

Nitrite NO2 water test in drops

What gets used up

Reagent bottles (bottles)2 bottles

Possible readings (measurements)50 measurements

Illustrated instructionsYes

What lasts for years

Screw-top glass test tubesYes

Sampling syringeYes

Grey comparator blockYes

Nine-field colour reading chartYes

Budget

Content of both columns taken from the manufacturer's official data sheet and instruction leaflet, on 07/09/2026.

Documents & manuals

Official manufacturer's instructions, in French

Six-step protocol, order of the two reagents, number of drops, and storage instructions. This is the instruction leaflet for the complete test: it applies equally to the refill, which contains the same reagents.

PDF · 3,1 Mo

Download

Estimate your
delivery time

0.08 kg parcel, dispatched within 48 hours by Colissimo or Chronopost to your home, as you choose at checkout. Both bottles are shipped in their original blister pack, which carries the EAN code and the batch number. The exact amount of the delivery charge is shown in the basket.

Frequently asked questions

6 questions

6 key questions

How long does a nitrite refill last?

50tests per refill

32 wksfirst year, cycling monitored day by day

47 wksestablished tank, one test per week

The calculation is based on the recommended frequency: one test per day for the first 3 weeks of a new freshwater setup, that is 21 tests, then one per week. A first year managed this way uses up the 50 tests around week 32, slightly sooner if you introduce several batches of fish. An established tank tested once a week, with a few extra tests after an incident, will last just under a year.

Do you need to replace nitrite reagents more often than the others?

Yes, and that is the one genuine peculiarity of this refill kit. Consumption rates vary enormously from one parameter to another.

Parameter	Actual frequency	Repurchase
Nitrite NO2	Daily at start-up, then weekly without interruption	Regular
Ammonium NH4	In bursts: at start-up, then nothing for months	Irregular
Copper Cu	Once after a treatment, sometimes never again	Rare

Nitrite is the only one of the three for which the recommended testing frequency never stops.

Why two bottles, and what does each one do?

Because the colour develops in two stages, and both reagents are added in the same order with each measurement.

Take reagent 1 and add 5 drops to the test tube containing the sample — never to the reference tube.
Take reagent 2 and add 5 drops immediately afterwards, to the same test tube.
Mix by gently swirling after each addition, then leave to stand for 5 minutes.

Both bottles are therefore used up at the same rate, and the refill replaces them together.

How many drops are needed per measurement?

Can an aged reagent give a false reading?

A degraded reagent produces a paler colour, giving a falsely low reading. The risk is being reassured when nitrite is actually present.

The check takes a minute: test a sample whose condition you already know — for example, right after a significant water change on a healthy tank — and compare it with the result from the previous time. A noticeably weaker colour than expected on water that has not changed points to the reagents, not the tank.

What precautions should be taken with these two bottles?

Reagent 1 is classified Danger, with hazard statements H314 and H318: causes severe skin burns and eye damage. If splashed in the eye, rinse immediately and thoroughly with the eyelid held open.

Reagent 2 carries statements H226 and H319, flammable liquid and eye irritation: keep the box away from any naked flame. Both caps are child-resistant and must be screwed back on fully; a bottle lying on its side on a shelf will eventually seep along the dropper. Store the box in a dry place at room temperature, in its original packaging.

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Reagent refill for NO2 nitrite test

The summary