Blister pack for the JBL PROAQUATEST KH refill, a carbonate hardness titration reagent bottle

Bottle of JBL ProAquaTest KH carbonate hardness reagent supplied in the refill, photographed on its own on a white background

Reagent refill for KH carbonate hardness test

Name: Reagent refill for KH carbonate hardness test
Brand: JBL
SKU: J2411100
Price: 5.9 EUR
Availability: InStock

5,90 €

This bottle is the titration reagent for the carbonate hardness test, sold separately. You add it drop by drop to 5 ml of water until the colour changes from blue to orange-yellow.

The number of drops added gives the result directly, at a rate of 1 °dKH per drop. The test tube from your kit remains in use, and there is no colour chart to replace with a titration method.

Ref. J2411100·Reagent refill

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The summary

What it measures: carbonate hardness, that is, the buffering capacity of your water.
What the box contains: 1 bottle of titration reagent.
How to read the result: you count the drops until the colour change, with no colour chart.
How many tests: the softer your water, the more tests you get, as each degree costs one drop.
What you are aiming for: 5 to 16 °dKH in freshwater, at least 5 in a pond.
A corrosive bottle: titrate over a sink; a drop of reagent never falls into the fish water.

The titration bottle on its own, one drop equals 1 °dKH per 5 ml of water

This refill is the titration bottle only for the KH carbonate hardness drop test: each drop added to 5 ml of water equals 1 °dKH, until the colour changes from blue to orange-yellow. Keep the test tube from the kit. Aim for at least 5 °dKH, and titrate over a sink: this corrosive reagent must never go into the fish's water.

Carbonate hardness, or KH, measures the hydrogen carbonates dissolved in your water, that is, its capacity to neutralise acids without the pH shifting. This bottle is the titration reagent alone for the KH drop test, and it is used with the test tube in your kit.

🔢 One drop, one degree

You fill the test tube with 5 ml of water, then add the reagent drop by drop, shaking after each drop, until the colour changes from blue to orange-yellow. The number of drops added gives the carbonate hardness directly in German degrees, so no colour chart is involved. One drop also corresponds to 1.78 °fH, to an alkalinity of 0.36 mmol/L and to 21.8 mg/L of hydrogen carbonates, which lets you compare your result with a mains water analysis.

In 10 ml of water

When the sample volume is doubled, each drop is worth only 0.5 dKH, which gives a finer reading on freshwater.

A bottle to suit your water

A test uses as many drops as the water has degrees, so soft water uses up the bottle more slowly.

🦠 A reserve that bacteria consume

Most freshwater fish and plants do well between 5 and 16 dKH, and a garden pond needs at least 5 dKH. In aquaponics, this reserve declines on its own, because the bacteria that convert ammonium into nitrate consume alkalinity, about 7.14 mg/L expressed as calcium carbonate for every milligram per litre of ammonia nitrogen. The more feed the fish are given, the more often this measurement should be taken, and the guide to the nitrogen cycle explains this reaction in detail.

The first turn towards yellow ends the count

Stop counting at the first drop that turns the colour to orange-yellow, not when the yellow becomes clear-cut. Shake after every drop, otherwise the colour change appears too late and your result comes out too high. Also take care not to confuse this bottle with the total hardness reagent, whose colour change goes from red to green.

Raising alkalinity with potassium bicarbonate

When your reading falls below 5 °dKH, potassium bicarbonate raises carbonate hardness while also supplying potassium to the crops, which often lack it in aquaponics. Add it in small amounts, then repeat the titration the next day with the same bottle to check the effect. The pH test completes the picture, as it shows the pH that your carbonate hardness maintains.

🧯 A corrosive and flammable reagent

The reagent is classified Danger, with hazard statements H314 and H226: it causes severe skin burns and eye damage, and it is a flammable liquid. So work over a sink, screw the child-resistant cap back on after each series, and store the bottle in a dry place, at room temperature, in its original packaging. Always hold it vertically, nozzle pointing down and dry on the outside, because a drop that comes out with a bubble counts as a whole drop and throws your result off by one degree.

Unopened, the KH reagent keeps for 3 years, but an opened bottle deteriorates faster on contact with air, which is why it is worth writing the opening date on the label. Order the refill as soon as the level drops noticeably, because hard water uses one drop per degree and empties the bottle faster than soft water. You keep the test tube from your carbonate hardness drop test, and the titrated sample goes down the sink: this reagent never goes into the fish's water.

Technical specifications

What the refill contains

Contents: 1 bottle of reagentKH titration reagent, child-resistant cap
Matching test: KH carbonate hardness test, ref. 2411000The refill is used with the test tube from this test
Manufacturer's reference: JBL 2411100, PROAQUATEST rangeNot to be confused with 2411000, which is the complete kit
Tests per bottle: Depending on water hardnessEach test uses as many drops as the water has degrees of hardness

Counting the drops

Value of one drop: 1 dKH per 5 mlIn 10 ml, one drop equals 0.5 °dKH
Colour change: From blue to orange-yellowStop at the first drop that makes the colour change

Hazard labelling

Signal word: DangerSingle bottle, with a child-resistant cap
Pictograms: Flame and corrosion
Hazard statements: H226, H314Flammable liquid, causes severe skin burns and eye damage
Precautionary statements: P101, P102, P303+P361+P353, P305+P351+P338, P501
Precautions: Sink, ventilated room, out of reachDeclared ethanol, 10 to 25%
Storage: 3 years, bottle unopenedAn opened bottle deteriorates faster when exposed to air

To allow for in addition

Test tube: The one for the carbonate hardness testFilled to 5 ml, or to 10 ml to read to the half degree
What you need to raise KH: Potassium bicarbonateIt raises alkalinity while supplying potassium to the plants

6 further specifications are available in the detailed view.

In the box

1 bottle of KH titration reagent, with child-resistant cap

Manufacturer's values (KH test instructions, safety data sheet and FAQ). The alkalinity consumed by nitrification, 7.14 mg/L as CaCO3 per mg/L of ammonia nitrogen, is a standard value in water treatment.

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.

The KH reagent on its own, or the whole kit?

The titration uses the same reagent. The kit adds the graduated test tube, which lasts as long as it stays clear.

One drop per degree, in 5 ml measured out The titration has no colour chart: its accuracy depends on the volume of water, and therefore on the graduated test tube.

	Titration bottles (bottle)	Graduated test tube from 5 to 20 ml	Price
Recommended Reagent refill for KH carbonate hardnessYour choice	1 bottle	No	5,90 €
KH water test, carbonate hardness, drop-basedYour choice	1 bottle	Yes	9,90 €

Reagent refill for KH carbonate hardnessRecommended

What runs out

Titration bottles (bottle)1 bottle

What keeps

Graduated test tube from 5 to 20 mlNo

Budget

KH water test, carbonate hardness, drop-based

What runs out

Titration bottles (bottle)1 bottle

What keeps

Graduated test tube from 5 to 20 mlYes

Budget

Contents of the two boxes based on the instructions of the carbonate hardness test.

Documents & manuals

Official manufacturer's instructions, in French

Full titration test protocol, reference volume and endpoint reading rule. This is the kit's instruction leaflet: it applies equally to the refill, which contains the same reagent.

PDF · 1,5 Mo

Download

Estimate your
delivery time

Parcel weighing 0.02 kg, dispatched within 48 h by Colissimo or Chronopost to your home, as you choose during checkout. The bottle is sent in its original packaging. The exact shipping 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

Why does the number of tests depend on my water?

Because it is a titration. Each measurement uses as many drops as the water has degrees, so soft water uses up the bottle slowly and hard water uses it up quickly.

Your water	Drops per measurement
Soft water, 5 °dKH	5
Medium water, 8 °dKH	8
Hard water, 16 °dKH	16

The same bottle therefore gives roughly three times as many measurements on the first water as on the third.

What carbonate hardness should you aim for?

Should you correct the KH before the pH?

My water analysis gives a TAC in °f, how do I compare?

Divide the value in French degrees by 1.78 to get German degrees, since one drop of this reagent equals 1 °dKH, or 1.78 °fH.

Your local water analysis	Expected drops
TAC 9 °f	5
TAC 18 °f	10
TAC 28 °f	16

One drop also corresponds to an alkalinity of 0.36 mmol/L, the unit used in some laboratory analyses.

Is the test tube included in the refill?

No. The refill contains only the reagent bottle, and the test tube is the one from your kit, filled to 5 ml so that one drop equals 1 °dKH.

If it is broken or no longer legible, get the complete carbonate hardness test rather than improvising with a measuring cup.

Rinse this test tube with clean water after each titration, over a sink, as the KH reagent must never go into the fish's water.

Why does alkalinity drop on its own?

Because nitrification consumes it. The bacteria that convert ammonium into nitrate use roughly 7.14 mg/L of alkalinity, expressed as calcium carbonate, for every milligram per litre of ammoniacal nitrogen processed, a standard figure in water treatment.

In a system where the fish receive a generous ration, this consumption is continuous, so this parameter should be monitored routinely and not just at start-up. The guide to the nitrogen cycle explains the reaction in detail.

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Reagent refill for KH carbonate hardness test

The summary