Box of the nitrite NO2 drop water test, on a white background

Contents of the nitrite kit: grey comparator block, two glass test tubes, syringe, two reagent bottles and colour chart

Nitrite reading: comparator block placed on the nine-field colour chart

The two reagent bottles from the nitrite test, numbered 1 and 2

JBL ProAquaTest nitrite NO2 drop water test

Name: JBL ProAquaTest nitrite NO2 drop water test
Brand: JBL
Price: 13.9 EUR
Availability: InStock

13,90 €

Nitrite is, along with ammonia, one of the two toxic compounds in a new tank. It appears after the ammonium, when the first family of bacteria is already active and the second is not yet established, and it blocks the transport of oxygen in your fish's blood.

This test measures it from 0.025 to 1 mg/L after 5 minutes, across nine colour fields, in freshwater as in seawater.

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The summary

What you receive: 2 reagent bottles, 2 glass test tubes, a syringe, a grey comparator block and a colour chart.
What nitrite does: it oxidises haemoglobin and blocks oxygen transport. A fish can suffocate in perfectly oxygenated water.
The threshold that matters: 0.5 to 1 mg/L can already be lethal depending on the species, and fry are more sensitive to it than adults.
How long it takes: 7 minutes in total, including 5 minutes waiting for the colour to develop.
How to choose: this is the bottle you empty first in a test kit, because it's the one you reach for most often.
What we send you: a parcel weighing 0.15 kg, reagents in their original packaging.

Nitrite drop test, from 0.025 to 1 mg/L, read in 5 minutes, with a target of zero

The JBL nitrite NO2 water test in drops (PROAQUATEST range) is used to monitor nitrite, which is toxic to fish because it blocks oxygen transport. It measures from 0.025 to 1 mg/L after a 5-minute wait, in freshwater as in seawater. The target is zero; from 0.5 mg/L the danger is real.

Nitrite can be neither seen nor smelled. It always appears at the same point: a few days after ammonium, once the bacteria that convert ammonium into nitrite have settled in and the ones that convert nitrite into nitrate are not yet numerous enough. This is the nitrite spike, and it accounts for a large share of the deaths in the first 3 weeks of a new tank.

🩸 Nitrite and haemoglobin

Nitrite uses the chloride ion transporter at the gills, builds up in the plasma to as much as 60 times the concentration in the water, then oxidises the iron in haemoglobin. This turns into methaemoglobin, which no longer binds oxygen, and the blood takes on a brown colour. Your fish may therefore gasp at the surface and die of asphyxiation in water saturated with oxygen, because the oxygen in the water is no longer carried to their tissues.

Since nitrite enters through the chloride transporter, dissolved chloride competes directly with it. Adding salt is therefore the only measure that protects your fish without changing the nitrite level in the water. Relative to the value read by this test, expressed as NO2, the fish-farming rule of thumb is roughly 2.5 mg/L of chloride per mg/L of nitrite for cyprinids, and roughly 5 for salmonids, which are more sensitive. Use non-iodised salt without anti-caking agents, dissolved separately, and never in an invertebrate tank or on a system that feeds crops.

Sensitivity varies enormously depending on the species

Depending on the species, concentrations between 0.5 and 1 mg/L can already be lethal, and marine fish as well as fry are particularly sensitive to them. Trout, salmon and catfish are the most fragile; carp, tench and eels are much more tolerant. A level that a koi carp can withstand can therefore kill a trout in the same pond.

📈 Where your cycling stands

The only comfortable value is zero. Unlike nitrate, there is no acceptable range: any readable value means that nitrification is not converting all the nitrite produced, and the first useful action is to change about half the volume while the bacteria recolonise the filter. The things that trigger a spike, such as fish added before cycling is complete or in too large a number, are described in the article on common mistakes.

Read nitrite alongside the ammonium result from the same day

If you are starting up a tank or a system, get the ammonium test at the same time as this one. Nitrite alone does not tell you where your cycling stands, whereas the two values read together do: ammonium falling while nitrite rises shows that the first family of bacteria is in place. You will thus know whether you need to wait longer before introducing fish, instead of finding out from their behaviour.

Nitrite rising, ammonium falling

This is the normal sequence of cycling. Measure every day and do not introduce fish.

Ammonium and nitrite both high

Cycling is in its early stages: the first family of bacteria is active, the second not yet. The same situation follows a disturbance, such as a filter rinsed under the tap or a pump that has been switched off.

Nitrite returning in an established tank

This situation is never normal; the usual causes are a sudden addition to the stock, overfeeding, a dead fish, or a blocked filter.

In aquaponics

A value readable on an established system indicates that your biofilter is undersized for the fish load.

❄️ Nitrite when the water cools down

In autumn, the activity of the nitrifying bacteria slows down with the water temperature, while the fish are still receiving their ration. A food that is too rich in protein then produces more ammonium than the biofilter can convert, and the nitrite level rises dangerously in a pond that stayed stable all summer. So switch to a wheat-germ winter food, lower in protein, as soon as the water cools, as explained in the article on feeding fish in winter. An aquaponic system goes through the same transition, and one reading a week is enough to follow it.

The test also works on cold water, but the colour develops more slowly, sometimes with a significant delay. So store the reagents at room temperature, between 20 and 25 °C, and let your sample stand for about 2 hours in a heated room before testing. If you get two inconsistent measurements at different temperatures, keep the higher one.

Technical specifications

The essentials

Parameter measured: Nitrite, expressed as NO2The intermediate between ammonium and nitrate in the nitrogen cycle
Measurement range: 0.025 to 1 mg/LThe target is zero: unlike nitrate, no readable value is comfortable
The colour chart fields: 0,01 · 0,025 · 0,05 · 0,1 · 0,2 · 0,4 · 0,6 · 0,8 · 1,0Nine values, from yellow to pink. The first field, 0.01, falls below the measurement range
Danger threshold: 0.5 to 1 mg/L depending on the speciesFry and marine fish are the most sensitive to it
Tests per kit: Approximately 50It is the first bottle you empty in a test kit, because it is the routine cycling test.
Manufacturer's reference: JBL 2412300, PROAQUATEST rangeCode EAN 4014162241238

The procedure

Water volume: 2 times 5 mlOne treated sample and one untreated blank, side by side in the comparator block
The steps: Rinse, fill, add reagent 1, add reagent 2, wait, readAdd 5 drops of each reagent, swirling after each addition
Waiting time: 5 minutesFull colour development time
Total duration: Approximately 7 minutesHandling included
Reading: In the comparison blockThe grey block compensates for the natural colour of the water, including peat
Environments covered: Freshwater and saltwaterOne measurement per day for 3 weeks on a new freshwater tank, one per week in saltwater

Security and parcels

Ranking: DangerBoth bottles are classified, and reagent 2 is flammable
Main risks: Burns, eye injuriesH314 and H318 hazard statements for reagent 1, H226 and H319 for reagent 2
Precautions: Sink, well-ventilated room, out of reachChild-safety caps on both bottles
Parcel weight: 0.15 kgPackaging included

To budget for separately

The matching test: An ammonium testThe two readings taken together show how far along your cycling is
Reagent refill: Reagents only, ref. 2412400The glassware, comparator block and colour chart can be kept

10 further specifications are available in the detailed view.

In the box

2 reagent bottles with child-resistant caps
2 glass test tubes with screw caps
1 graduated sampling syringe
1 grey laboratory comparator block
1 colour chart with 9 colour fields
1 multilingual instruction leaflet, French included

Reference, EAN code, kit contents, number of measures, protocol, mortality threshold and hazard statements taken from the manufacturer's data sheet and instructions on 05/09/2026. The range and the nine fields are read from the supplied colour chart. The chloride-to-nitrite ratios, converted to NO2 from the EIFAC recommendation expressed as nitrite nitrogen, and the plasma concentration factor come from the aquaculture veterinary literature.

Manufacturer and product safety

Manufacturer: JBL GmbH & Co. KG
Postal address: Dieselstraße 3, 67141 Neuhofen, Allemagne
Contact: info@jbl.de
Website: www.jbl.de

Information provided under Regulation (EU) 2023/988 on general product safety.

Nitrite alone, or the entire nitrogen sequence?

Nitrite comes after ammonium and converts into nitrate. The question is whether you want to see one stage of the chain or the whole sequence.

The nitrite peak occurs in the middle of the cycle Nitrite rises as ammonium falls, and it can be read on its own or as part of the full NH4, NO2, NO3 sequence. What you need depends on where you are in the process.

	Parameters covered (parameters)	Drop tests included (tests)	Nitrite NO2, the most toxic stage	Ammonium NH4, the preceding stage	Nitrate NO3, the next stage	pH and KH, which govern bacterial activity	Iron, phosphates, copper, silicates, oxygen	Reagent bottles (bottles)	Glass test tubes	Laboratory comparator block	Thermometer	Reagent refill sold separately	Price
Recommended Nitrite test onlyYour choice	1 parameters	1 tests	Yes	No	No	No	No	2 bottles	2	Yes	No	Yes	13,90 €
6-in-1 Aquarium Water Testing KitYour choice	6 parameters	5 tests	Yes	Yes	Yes	Yes	No	9 bottles	3	Yes	No	Yes	50,90 €
13-in-1 water testing kit for aquariumsYour choice	12 parameters	13 tests	Yes	Yes	Yes	Yes	Yes	23 bottles	12	Yes	Yes	Yes	99,90 €

Nitrite test onlyRecommended

The nitrogen cycle

Parameters covered (parameters)1 parameters

Drop tests included (tests)1 tests

Nitrite NO2, the most toxic stageYes

Ammonium NH4, the preceding stageNo

Nitrate NO3, the next stageNo

pH and KH, which govern bacterial activityNo

Iron, phosphates, copper, silicates, oxygenNo

Equipment supplied

Reagent bottles (bottles)2 bottles

Glass test tubes2

Laboratory comparator blockYes

ThermometerNo

Budget

Reagent refill sold separatelyYes

6-in-1 Aquarium Water Testing Kit

The nitrogen cycle

Parameters covered (parameters)6 parameters

Drop tests included (tests)5 tests

Nitrite NO2, the most toxic stageYes

Ammonium NH4, the preceding stageYes

Nitrate NO3, the next stageYes

pH and KH, which govern bacterial activityYes

Iron, phosphates, copper, silicates, oxygenNo

Equipment supplied

Reagent bottles (bottles)9 bottles

Glass test tubes3

Laboratory comparator blockYes

ThermometerNo

Budget

Reagent refill sold separatelyYes

13-in-1 water testing kit for aquariums

The nitrogen cycle

Parameters covered (parameters)12 parameters

Drop tests included (tests)13 tests

Nitrite NO2, the most toxic stageYes

Ammonium NH4, the preceding stageYes

Nitrate NO3, the next stageYes

pH and KH, which govern bacterial activityYes

Iron, phosphates, copper, silicates, oxygenYes

Equipment supplied

Reagent bottles (bottles)23 bottles

Glass test tubes12

Laboratory comparator blockYes

ThermometerYes

Budget

Reagent refill sold separatelyYes

Parameters covered, equipment supplied and kit contents noted from the three product pages on 05/09/2026.

Documents & manuals

Official manufacturer's instructions, in French

Six-step protocol, number of drops, colour development time, mortality threshold by species, and what to do if a reading is high.

PDF · 3,1 Mo

Download

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delivery time

Parcel weighing 0.15 kg, dispatched within 48 h by Colissimo or Chronopost to your home, as you choose during checkout. The reagents travel upright, in their original box. The exact cost is shown in your basket. Once unsealed, this product cannot be returned under the right of withdrawal (article L221-28, 5° of the French Consumer Code), for reasons of hygiene and health protection.

Frequently asked questions

6 questions

6 key questions

How long does a nitrite spike last?

My fish are breathing at the surface even though the water is well oxygenated — why?

At what level does nitrite become lethal?

How do you bring nitrite levels down quickly?

Change about half of the volume, using water with a pH close to that of the tank.
Add chloride in the form of non-iodised salt, dissolved separately, never when invertebrates or crops are present.
Stop feeding for 2 days, and remove anything that is decomposing.
Leave the filter alone: this is where the missing bacteria develop.

Salt does not lower the nitrite in the water, it only limits its uptake into the fish's blood.

The spike has passed — can I add my fish now?

In aquaponics, should you also aim for zero?

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JBL ProAquaTest nitrite NO2 drop water test

The summary