Blister pack for the JBL PROAQUATEST O2 refill, three numbered reagent bottles 1, 2 and 3

Reagent refill for dissolved oxygen test

Name: Reagent refill for dissolved oxygen test
Brand: Hardy Dewerse
SKU: J2411300
Price: 9.2 EUR
Availability: InStock

9,20 €

3,06 € × 3 with no fees Klarna.

These three bottles are the reagents for the dissolved oxygen test, providing approximately 40 measurements. Each measurement uses 6 drops from each of the three bottles.

The method fixes the oxygen in the test tube at the moment of sampling, then reveals it through a colour reaction. The glass test tube, its screw cap, the syringe, and the colour chart from your kit remain in use throughout.

Ref. J2411300·Reagent refill

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The summary

What it measures: the oxygen actually dissolved in the water, in milligrams per litre.
What the box contains: 3 numbered reagent bottles, 1, 2, and 3.
Number of tests: approximately 40, at 6 drops from each bottle.
When to test: early in the morning in summer, when the curve is at its lowest.
The alert threshold: below 5 mg/L first thing in the morning, aeration should be increased the same day.
Refill or complete kit: the refill is sufficient if your test tube still seals without leaking and your colour chart shows shades of red.

Reagents 1, 2 and 3 for the oxygen test, approximately 40 measurements, from 1 to 10 mg/L

Dissolved oxygen leaves the water the moment it is poured or agitated, which is why this test fixes it chemically inside the test tube at the very moment of sampling, before revealing it through a colour change. These three numbered bottles, 1, 2 and 3, are the reagents for this process, providing approximately 40 measurements between 1 and 10 mg/L.

🧪 Three reagents in order

Fill the test tube to the brim by submerging it in the water, then slowly add 6 drops of reagent 1 and 6 drops of reagent 2, allowing it to overflow slightly. Seal it without trapping any air bubbles and shake vigorously for approximately 30 seconds. Only then do you add 6 drops of reagent 3, reseal and shake again for 30 seconds, at this stage an air bubble no longer affects the result. After 10 minutes, lay the test tube on its side and move it back and forth 3 to 5 cm above the white section of the colour chart, whose shades range from yellow to dark red.

🐟 Three oxygen consumers

Fish are not the only organisms consuming oxygen in your water: the bacteria in the filter also need oxygen to convert ammonium into nitrate, and the roots of your crops consume it too. In aquaponics, the working range is between 5 and 8 mg/L. The amount of oxygen water can dissolve decreases as temperature rises, whilst plants in light can exceed saturation by 1 to 2 mg/L by the end of the day. Measure early in the morning, when the value is at its lowest, and the guide to maintaining your system in summer sets out the key actions for that period.

An air pump when the morning reading drops

If your morning reading drops below 5 mg/L, an aquarium air pump with one or two outlets increases gas exchange at the surface, where water recharges with oxygen. Take another reading the following morning at the same time to check the effect of the aeration. For a pond, the complete pond aerator performs the same role over a larger volume.

The three-bottle refill follows the red colour chart

This refill is intended for the current oxygen test, which uses three reagents and a colour chart in shades of red. An older two-reagent kit came with a colour chart in beige tones, and these new bottles cannot be read against it. Please check the colour of your chart before ordering: if it is beige, you need the complete oxygen test.

All three reagents are classified Danger, with hazard statements H314 and H318, indicating serious skin burns and eye damage. Reagent 1 also carries statements H373 and H412, and Reagent 3 carries H317 and H334, indicating a risk of skin and respiratory sensitisation. Work over a sink in a well-ventilated room, keep your face away from any treated test tube, and empty it down the sink rather than into your tank.

📆 40 tests, a complete set

Each measurement uses 18 drops, 6 from each of the three bottles, which accounts for the count of approximately 40 measurements. At the recommended rate of one measurement per week for a new water setup, plus an extra one whenever your fish show signs of oxygen deficiency, the kit covers several months of monitoring. Store the three capped bottles in a dry place at room temperature in their original packaging, and replace them all together, as they are used at the same rate.

Technical specifications

What the refill contains

Contents: 3 reagent bottlesReagents 1, 2 and 3, numbered on the label
Measurements: Approximately 40Six drops from each bottle per measurement, making 18 drops in total.
Reading range: 1 to 10 mg/LIn freshwater, milligrams per litre is equivalent to ppm
Target values: 5 to 8 mg/LWorking range in aquaponics. Saturation decreases as the water warms up
Manufacturer's reference: JBL 2411300, PROAQUATEST rangeNot to be confused with 2411200, which is the complete test kit
Hazard classification: Danger, all 3 bottlesH314 and H318 on all three, H373 and H412 on reagent 1, H317 and H334 on reagent 3

To budget for separately

Test tube with screw cap: Those from the oxygen testThe test tube is filled by immersion and sealed as it overflows, with no air trapped inside
Colour comparison chart: The one from the oxygen testThe current colour chart, in shades of red, corresponds to the three reagents

In the box

3 reagent bottles, numbered 1, 2 and 3

Reference, EAN code, contents, protocol, number of tests and hazard statements taken from the JBL data sheet and instructions on 07/10/2026. Saturation by temperature: table from the JBL instructions. Range of 5 to 8 mg/L: FAO, small-scale aquaponics, 2014.

Top up the reagents, or replace the kit?

Three bottles on one side, the same three bottles plus the glassware on the other. What tips the balance is the condition of what you keep from one year to the next.

An oxygen reading depends on an airtight seal The three reagents will not give an accurate result if the test tube lets a bubble in when closing, or if the white background of the colour chart has yellowed.

	Reagent bottles (bottles)	Possible readings (measurements)	Glass test tube with screw cap	Graduated sampling syringe	Red colour chart with white section	Price
Recommended Reagent refill for dissolved oxygen testYour choice	3 bottles	40 measurements	No	No	No	9,20 €
Dissolved oxygen water test in dropsYour choice	3 bottles	40 measurements	Yes	Yes	Yes	14,90 €

Reagent refill for dissolved oxygen testRecommended

What gets used up

Reagent bottles (bottles)3 bottles

Possible readings (measurements)40 measurements

What keeps well

Glass test tube with screw capNo

Graduated sampling syringeNo

Red colour chart with white sectionNo

Budget

Dissolved oxygen water test in drops

What gets used up

Reagent bottles (bottles)3 bottles

Possible readings (measurements)40 measurements

What keeps well

Glass test tube with screw capYes

Graduated sampling syringeYes

Red colour chart with white sectionYes

Budget

Contents of both columns taken from the supplier's data sheet and instruction leaflet, on 05/09/2026.

Estimate your
delivery time

Parcel weight 0.08 kg, dispatched to a collection point or to your home address — your choice at checkout. All three bottles are sent in their original packaging. The exact shipping cost is shown in the basket.

Frequently asked questions

6 questions

6 key questions

Why does the test tube fill by submersion?

What time of day should you take a reading?

Measure first thing in the morning, before daybreak if possible. Dissolved oxygen follows a 24-hour curve: its concentration rises as long as plants and algae receive light, then falls during darkness, since fish, bacteria, and plants continue to respire.

A reading taken in the middle of the afternoon therefore gives the best value of the day, and says nothing about the lowest value, which is reached before dawn.

What level can the water reach depending on its temperature?

Temperature	Saturation
10 °C	10.9 mg/L
16 °C	9.6 mg/L
20 °C	8.9 mg/L
24 °C	8.3 mg/L
28 °C	7.8 mg/L

Water at 28 °C cannot exceed 7.8 mg/L without the help of plants, which leaves little headroom above 5 mg/L. A well-planted tank can exceed saturation by 1 to 2 mg/L at the end of the lighting period.

What should be done if the morning reading drops below 5 mg/L?

Does an air bubble in the test tube affect the reading?

Yes, and it is the most common mistake with this test. A bubble trapped before reagent 3 is added exchanges with the water during the first agitation, and the reading comes out higher than the actual value. Once reagent 3 has been added, the oxygen is fixed and a bubble has no further effect.

The check takes only a glance: before screwing the cap on, hold the test tube to the side and look through it — it should be slightly overfull. If a bubble remains, empty it and start again rather than trying to dislodge it by tapping.

What precautions should you take with these three bottles?

All three reagents are classified as Danger, with hazard statements H314 and H318: severe skin burns and eye damage. If a splash reaches the eye, rinse immediately and thoroughly with the eyelid held open.

Reagent 1 also carries statements H373 and H412, and reagent 3 carries H317 and H334, indicating skin and respiratory sensitisation. Work over a sink in a well-ventilated room, screw child-resistant caps back on firmly, and take empty bottles to a recycling centre with household chemicals.

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Reagent refill for dissolved oxygen test

The summary