Box for the dissolved oxygen O2 water test, 10.6 by 17.5 cm format, 40 x TEST stated on the packaging

Contents of the dissolved oxygen test: three reagent bottles, glass test tube with screw cap, syringe and colour reading chart.

Reading the colour chart of the dissolved oxygen test, held by hand at the water's edge

Dissolved oxygen test kit placed at the edge of a garden pond, box, reagent bottles and colour chart

Oxygen solubility curve in freshwater, from 0 to 35 degrees, at atmospheric pressure, with the typical summer temperature range of a garden pond

Dissolved oxygen O2 water test in drops

Name: Dissolved oxygen O2 water test in drops
Brand: JBL
Price: 16.91 USD
Availability: InStock

$16.91

A lack of oxygen can kill the fish in a pond in a single summer night. This test measures the actual dissolved oxygen, from 1 to 10 mg/L, in aquariums, ponds, and aquaponics systems.

The difficulty lies in the sampling: the test tube must be filled by immersion, to the brim, and the slightest trapped bubble will skew the result upwards.

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The summary

What you receive: 3 bottles of reagents, a glass test tube with a screw cap, a syringe and a colour chart.
What you measure: dissolved oxygen from 1 to 10 mg/L, in freshwater, seawater and ponds.
When to test: in the early morning, before sunrise, when oxygen is at its lowest of the day.
How long it takes: 12 minutes per test, 10 of which are waiting time.
How to choose: this test is sold on its own, and oxygen is also included in the 13-in-1 case for aquariums and in the 10-in-1 case for ponds.
Three corrosive reagents: they react in the screw-cap test tube, which you then empty down the sink; they never go into the fish water.

Dissolved oxygen drop test, from 1 to 10 mg/L, for aquariums, ponds, and aquaponics

This drop test reads dissolved oxygen from 1 to 10 mg/L, for about 40 measurements, in aquariums, ponds and aquaponics, where the FAO advises at least 5 mg/L. Measure in the early morning, when oxygen is at its lowest, using a test tube filled by immersion: the reagents never enter the fish water.

A rise in ammonium or nitrite develops over several days, whereas a lack of oxygen becomes dangerous within hours. A night spent in the red zone of the colour chart, at 2 mg/L or less, can be enough to kill the fish in a pond where nothing looked wrong the previous evening, because the level reaches its minimum just before dawn, at an hour when people rarely test. This test is therefore best done in the early morning, to catch the lowest value of the day.

🌞 Warm water, less oxygen

The amount of oxygen that water can dissolve depends first of all on its temperature. Saturated fresh water holds about 11 mg/L of oxygen at 10 °C, and less than 8 mg/L at 30 °C. A heatwave therefore hits your pond twice: it lowers the available ceiling while the heat speeds up the respiration of fish and bacteria, which then use more. This is the mechanism described in the guide to system maintenance in summer.

Break the surface as soon as oxygen drops below 4 mg/L

Aim for 5 to 8 mg/L in a freshwater community aquarium, and 5 to 10 mg/L in a lightly stocked planted tank, in seawater and in a pond. Below 4 mg/L, break the water surface: an air pump and its diffusers raise the level within a few hours, because they renew the water in contact with the air. Then check the nitrite over the following days, since nitrifying bacteria need oxygen to convert ammonium.

🌱 Oxygen in aquaponics

In an aquaponic system, three populations breathe the same water: the fish, the nitrifying bacteria in the biofilter and the plant roots. The bacteria need oxygen to convert ammonium into nitrate, so a lack of oxygen often shows up in nitrification before it shows in the fish. Aim for at least 5 mg/L in the fish tank and in the grow beds, and sample at the least agitated point, the end of a channel or the bottom of a media bed, rather than right next to the diffuser. Setting up a complete system is described in the article Getting an aquaponic system off to a good start.

A reading taken at the end of the day overestimates your oxygen

Plants and algae produce oxygen as long as there is light, and consume it all night without producing any. In a well-planted tank or pond, the level even exceeds saturation by 1 to 2 mg/L at the end of the lighting period. The maximum level is therefore reached in the late afternoon and the minimum just before sunrise, so a reading taken at the end of the day gives the highest value and says nothing about the lowest.

Garden pond in summer

Warm water, high biomass and short nights add up. Green water lowers the night-time minimum even further.

Aquaponics

The biofilter consumes oxygen continuously, in addition to the fish. Without oxygen, nitrification stops.

Planted tank with CO2 injection

Oxygen content drops at night, while gas injection sometimes carries on.

After a power cut

A pump stopped for a few hours, a medication, an algal bloom dying off all at once: each can make oxygen plunge within a day.

🫧 Fill without an air bubble

The sample for this test is not drawn with a syringe. Rinse the test tube, then fill it by immersion, right to the brim, and place it on a waterproof surface. Add the 6 drops of the first reagent and the 6 of the second slowly, allowing it to overflow, and screw on the cap without trapping a single bubble. These two reagents chemically fix the oxygen present at the moment of closing: a bubble trapped at this stage would add its own oxygen, and your result would be overestimated. After 30 seconds of shaking, the third reagent develops the colour, from yellow to dark red, and any bubbles trapped when closing the test tube no longer play any part.

⚗️ Three bottles to close straight away

All three reagents carry the Danger warning. The first contains manganese chloride, the second sodium hydroxide, and the third sulphuric acid and a phenylenediamine derivative that can cause an allergic reaction of the skin or respiratory tract. As the test tube is filled to the brim by immersion, add the drops over a sink, screw the cap back on without trapping any air, then shake while holding the tube closed. On a pond or an aquaponic system, never dip the bottle into the water and never pour the sample back after reading: it goes down the sink, and you rinse the tube. The O2 reagent refill replaces all three bottles.

Technical specifications

Measuring oxygen

Parameter measured: Dissolved oxygen in the waterThe method chemically fixes the oxygen present at the moment of sampling, then reveals it through a colour change from yellow to dark red
Measuring range: 1 to 10 mg/LIn fresh water, one milligram per litre is equivalent to one ppm
Tests per kit: Around 40Each measurement uses 6 drops from each of the 3 bottles, so 18 drops
Target values: 5 to 8 mg/L in freshwater5 to 10 mg/L in a lightly stocked planted tank, in seawater and in a pond. The colour chart turns red at 2 mg/L and below
Method: Chemical fixation, colorimetric readingManganese salt, strong base, then an acid developer: this is the principle behind laboratory oxygen assays
Manufacturer's reference: JBL 2411200, PROAQUATEST rangeEAN code 4014162241122

The procedure

Sampling: Test tube filled by immersionRight up to the rim, with no bubbles, and not with a syringe
The steps: Rinse, immerse, add reagent, shake, develop, readIn that order. The cap screws on while letting the test tube overflow
Drops per reagent: 6 drops, three times6 of reagent 1, 6 of reagent 2, then 6 of reagent 3 after the first shake
Shaking and waiting: 2 times 30 s, then 10 minReading before the 10 minutes are up underestimates the value
Total time: About 12 minutesHandling included
Reading: Test tube lying on its side, 3 to 5 cm from the colour chartMoved back and forth over the white section, until the colour matches as closely as possible

Hazard labelling

Signal word: DangerOn all three bottles
Pictograms: Corrosion and health hazardGHS05 on all three bottles, GHS08 on reagents 1 and 3
Hazard statements: H314, H373, H412, H317, H334Burns, organ damage from repeated exposure and aquatic toxicity (reagent 1), skin and respiratory allergy (reagent 3)
Precautionary statements: P101, P102, P303+P361+P353, P305+P351+P338, P501Label kept for medical advice, children kept away, skin and eyes rinsed with water, bottles disposed of according to local rules
Precautions: Sink, ventilated room, out of reachNever smell a bottle or a test tube, and empty the treated tube down the sink
Classified components: Manganese, soda, sulphuric acidManganese chloride, sodium hydroxide and sulphuric acid, one per bottle

To allow for in addition

Reagent refills: Reagents only, ref. 2411300The glass test tube, its stopper, the syringe and the colour chart keep
Enough to correct: An air pump and its diffusersBelow 4 mg/L at early morning, aeration is increased the same day

12 further specifications are available in the detailed view.

In the box

3 reagent bottles
1 glass test tube with a screw cap
1 graduated sampling syringe
1 reading chart with a white background
1 multilingual instruction leaflet, French included

Manufacturer's values (instructions, colour chart and safety data sheets for the three reagents). Aquaponic reference values from the FAO.

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.

Oxygen is not in every kit

It is a parameter that not all test kits include. Before buying a kit to measure it, check that it really does contain it.

Oxygen depletion occurs before daybreak At night, plants consume oxygen without producing any, and warm water holds less of it. A check carried out in the afternoon therefore does not reveal this minimum.

	Dissolved oxygen	Parameters covered	Drop test kits included	pH, KH, nitrite, nitrate and ammonium	GH, iron, phosphates, copper and silicates	Reagent bottles (bottles)	Glass test tubes	Screw-cap test tube	Thermometer	Reagent refill sold separately	Price
Recommended Dissolved oxygen test onlyYour choice	Yes	1	1	No	No	3 bottles	1	Yes	No	Yes	$16.91
6-in-1 Aquarium Water Testing KitYour choice	No	6	5	Yes	No	9 bottles	3	No	No	Yes	$57.77
JBL ProAquaTest Lab water analysis case, 13 tests for aquarium and pondYour choice	Yes	12	13	Yes	Yes	23 bottles	12	Yes	Yes	Yes	$113.38

Dissolved oxygen test onlyRecommended

What you are measuring

Dissolved oxygenYes

Parameters covered1

Drop test kits included1

pH, KH, nitrite, nitrate and ammoniumNo

GH, iron, phosphates, copper and silicatesNo

Equipment supplied

Reagent bottles (bottles)3 bottles

Glass test tubes1

Screw-cap test tubeYes

ThermometerNo

Budget

Reagent refill sold separatelyYes

6-in-1 Aquarium Water Testing Kit

What you are measuring

Dissolved oxygenNo

Parameters covered6

Drop test kits included5

pH, KH, nitrite, nitrate and ammoniumYes

GH, iron, phosphates, copper and silicatesNo

Equipment supplied

Reagent bottles (bottles)9 bottles

Glass test tubes3

Screw-cap test tubeNo

ThermometerNo

Budget

Reagent refill sold separatelyYes

JBL ProAquaTest Lab water analysis case, 13 tests for aquarium and pond

What you are measuring

Dissolved oxygenYes

Parameters covered12

Drop test kits included13

pH, KH, nitrite, nitrate and ammoniumYes

GH, iron, phosphates, copper and silicatesYes

Equipment supplied

Reagent bottles (bottles)23 bottles

Glass test tubes12

Screw-cap test tubeYes

ThermometerYes

Budget

Reagent refill sold separatelyYes

Parameters covered and equipment taken from the data sheets of this test and the two kits.

Documents & manuals

Official manufacturer's instructions, in French

The eight-step protocol, filling the test tube by immersion, and the oxygen saturation table as a function of temperature on the last page.

PDF · 1,5 Mo

Download

Estimate your
delivery time

Parcel of 0.11 kg, dispatched within 48 h by Colissimo or Chronopost home delivery, as you choose during payment. The reagents are sent in their original box. The exact amount is shown in the basket. Once unsealed, this product can no longer 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

Why do my fish come to gulp at the surface in the morning?

At what level should you start to worry?

How can I quickly increase the oxygen content?

Break the surface: an air pump, a waterfall, a jet aimed upwards.
Lower the temperature if you can, as cooler water holds more oxygen.
Stop feeding for 24 hours, since digestion uses oxygen.
Remove anything decomposing on the bottom, such as dead leaves and uneaten food.

Stirring up the water works faster than anything else, because it is the surface area in contact with the air that lets oxygen in, not the volume of bubbles.

Is an air stone enough for a pond?

It depends on the volume and the fish load, and the only way to find out is to measure at dawn before and after. An air stone rated at 600 L/h does a lot in 1,000 litres and very little in 10,000. What matters is not the stated air flow rate but the movement it gives to the whole water column: a diffuser placed at the deepest point circulates the water better than two diffusers placed at the edge.

I still have the old two-reagent test, is the refill suitable?

Does the test work in a garden pond?

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Dissolved oxygen O2 water test in drops

The summary