Blister pack for the JBL PROAQUATEST K refill, one liquid reagent and one powder reagent for the potassium test

Bottle and pot of JBL ProAquaTest potassium K reagents supplied in the refill, on a white background

Reagent refill for potassium K test

Name: Reagent refill for potassium K test
Brand: JBL
SKU: J2413100
Price: 2000.0 RSD
Availability: InStock

2,000.00 RSD

666.66 RSD × 3 with no fees Klarna.

Potassium is one of the nutrients that fish feed covers poorly, so it is often lacking in aquaponics. These two reagents are those of the potassium test, for about 25 measurements.

The result is read by turbidity, by pouring in until a printed cross disappears. The two tubes, the syringe, the double measuring spoon and the reading card from your kit remain in use.

Ref. J2413100·Reagent refill

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The summary

Two corrosive reagents: the tube is emptied down the sink after reading, never into the fish water.
What's in the box: 2 reagent bottles, one liquid and one powder.
How to read the result: a printed cross disappears, with no colour chart or shade comparison.
How many tests: about 25, the same count as the original kit.
What volume to take: 15 ml with the syringe, poured into the test tube.
Reagents only or the full test: the refill is enough if your two tubes and your reading card are intact.

Reagents K 1 and K 2, approximately 25 tests, result read by turbidity

This refill contains reagents K 1 and K 2 for the potassium drop test, one liquid and one powder, for about 25 measurements from 2 to 15 mg/L. Reading by turbidity requires the tubes, the syringe, the measuring spoon and the cross card from the kit. Both reagents are corrosive and never go into the fish water.

Potassium is one of the macronutrients that actively growing plants consume in the greatest quantities, and they take it up within a few hours. These two bottles, one liquid reagent and one powder reagent, are the reagents alone for the potassium test, for around 25 measurements in freshwater and, once diluted, in seawater.

This test does not compare any colour: the potassium forms a whitish cloudiness with the reagents, and it is the height of liquid needed to hide a printed cross that gives the content. The natural colour of your water therefore does not affect the reading, provided the water is clear to begin with, and you read the value directly on the measuring tube graduated in milligrams per litre.

🔬 A cross that disappears

Fill the measuring tube with 15 ml of water using the syringe, then add 10 drops of reagent 1 and mix. One level scoop of powder, taken with the wide end of the double measuring spoon, turns the water cloudy; shake gently for 30 seconds, leave to stand for 1 minute, then shake one last time. Placed on the cross on the card, the glass reading tube receives this mixture until the cross is no longer visible from above, and the graduation read at the bottom of the meniscus gives the level in mg/L.

The large measure of powder is levelled off when dosing

The powder reagent is taken with the wide end of the double measuring spoon, and a heaped dose skews the turbidity obtained. Level the spoon against the rim of the bottle before tipping it in, and dose away from any draught. A dosing error carries through to the reading, and then to the correction you draw from it.

Seawater

Dilute 10 ml of sample to 300 ml with distilled water, measure, then multiply the result by 30.

Glass sampling tube

The tube graduated in mg/L is available as a spare part, which saves you buying the whole kit again if it breaks.

A salt that supplies potassium and alkalinity

Choose potassium bicarbonate with the refill if your reading stays below 10 mg/L. It raises both the potassium level and the carbonate hardness in a single addition, which avoids correcting the same water twice. The carbonate hardness test lets you track the second value after each addition.

Both reagents are classified Danger, with the hazard statement H314, which indicates severe skin burns and eye damage. Measure out the powder over a sink, without blowing on the measuring spoon to level it, and rinse immediately and at length with water if any gets in the eye. Pour the treated test tube down the sink, never into your tank, and keep the bottles closed, dry, at room temperature and in their original packaging.

Both bottles are used with the tubes, the measuring spoon and the colour card of your potassium drop test; these reagents must never go into the fish water.

🌱 An element that feed covers poorly

Fish waste supplies mainly nitrogen and phosphorus, while potassium remains too scarce in it for the crops, so it is often lacking in an aquaponic system. For good growth, the level should be around 10 mg/L, and up to 30 mg/L under intense lighting. Beyond that, filamentous algae benefit, and too high a level becomes dangerous for sensitive animals such as shrimp. Our guide to plant deficiencies in aquaponics describes the dried or scorched leaf edges that signal this shortage.

⚖️ Correcting a low level

When the reading stays below 10 mg/L for several days in a row, in aquaponics potassium is most often supplied through the base already used to raise the pH. Nitrification acidifies the water continuously, so a potassium-based alkaline additive corrects both deficiencies in a single addition. Systems that also use a calcium-based additive alternate the two, so that neither calcium nor potassium runs short for the crops. Then measure the potassium 24 hours after the addition: the new value tells you whether the dose was enough or needs repeating.

📏 A schedule that spaces out

At start-up, measure potassium every day until you know how quickly your plants use it, then space out the checks once that rhythm is established. The 25 tests in the refill are therefore concentrated in the first few weeks, whereas a stabilised system makes them last much longer. Always take your sample at the same time of day, since your plants absorb potassium within a few hours and a reading taken just after an addition cannot be compared with the previous day's.

Technical specifications

What the refill contains

Contents: 2 reagent bottlesOne liquid reagent and one powdered reagent, numbered on the label
Readings: Around 25As much reagent as in the full test
Manufacturer's reference: JBL 2413100, PROAQUATEST rangeNot to be confused with 2413000, which is the complete kit
Matching test: Potassium K test, ref. 2413000The refill is used with the tubes, the syringe, the measuring spoon and the card of this test

Measuring potassium

Reading principle: Turbidity, not colourPotassium precipitates as a whitish suspension, and it is the resulting cloudiness that gives the value
Sample volume: 15 ml per measureMeasured with the syringe, in the plastic measuring tube
Reagents to be measured out: 10 drops and 1 level large measureLarge end of the double measuring spoon for the powder
Time per test: About 4 minutes30 seconds of shaking, 1 minute of rest, then pouring
Water types covered: Freshwater, seawaterIn seawater, 10 ml diluted to 300 ml, result multiplied by 30
Parcel weight: 0.08 kgPackaging included

Hazard labelling

Signal word: DangerThe 2 bottles are ranked, with child-resistant caps
Pictograms: Corrosive, GHS05
Hazard statements: H314Severe skin burns and eye damage
Precautionary statements: P101, P102, P303+P361+P353, P305+P351+P338, P501
Precautions: Sink, ventilated room, out of reachSodium hydroxide (K 1), sodium carbonate and sodium tetraphenylborate (K 2)
Storage: Dry, at room temperatureBottles tightly closed, in their original packaging

To allow for in addition

Tubes, syringe and measuring spoon: Those from the potassium testThe sampling tube is graduated in milligrams per litre, and it is this that displays the result
Reading card: The one from the potassium testIt bears the reference cross, without which the pour cannot be read

10 further specifications are available in the detailed view.

In the box

2 bottles: liquid reagent K 1 and powdered reagent K 2

Manufacturer's values (K test instructions, safety data sheets and FAQ). Dilution beyond the graduation and the reading tube as a spare part: manufacturer's FAQ.

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.

Two bottles, or the complete kit?

The refill and the kit contain the same reagent, the same protocol and the same number of tests. The choice depends on the tubes, the measuring scoop and the reading card you already have.

Turbidity is read against a card, not a colour chart Reading the result requires the reference cross, the test tube graduated in milligrams per litre and the measuring scoop that doses the powder.

	Reagent bottles (bottles)	Possible tests (tests)	Plastic measuring tube	Glass sampling tube	Sampling syringe	Double measuring scoop	Cross-reading card	Price
Recommended Reagent refill for potassium K testYour choice	2 bottles	25 tests	No	No	No	No	No	2,000.00 RSD
Potassium K water test in dropsYour choice	2 bottles	25 tests	Yes	Yes	Yes	Yes	Yes	2,800.00 RSD

Reagent refill for potassium K testRecommended

What runs out

Reagent bottles (bottles)2 bottles

Possible tests (tests)25 tests

What keeps

Plastic measuring tubeNo

Glass sampling tubeNo

Sampling syringeNo

Double measuring scoopNo

Cross-reading cardNo

Budget

Potassium K water test in drops

What runs out

Reagent bottles (bottles)2 bottles

Possible tests (tests)25 tests

What keeps

Plastic measuring tubeYes

Glass sampling tubeYes

Sampling syringeYes

Double measuring scoopYes

Cross-reading cardYes

Budget

Contents of the two boxes, taken from the instructions and the data sheet for the potassium test.

Estimate your
delivery time

A 0.08 kg parcel, dispatched within 48 hours by Colissimo or Chronopost home delivery, as you choose at checkout. The bottles are sent in their 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

8 questions

6 key questions, 8 in the detailed view

Why does this test need 15 ml of water?

How do you read a result without a colour chart?

Place the measuring tube on the printed cross on the reading card.
Pour the cloudy mixture in gently, looking down through the top of the tube.
Stop at the exact moment the cross is no longer visible.
Read the graduation at the bottom edge of the meniscus, in bright, diffuse light.

The value is therefore not a shade compared against a chart but a height of liquid, which makes this test unaffected by the colour of your water.

What should you do if the value goes beyond the graduation on the tube?

Dilute the sample with distilled water up to 15 ml, repeat the measurement, then multiply the result.

Your water	Distilled water	Factor
7.5 ml	7.5 ml	× 2
3 ml	12 ml	× 5
1.5 ml	13.5 ml	× 10

In seawater, dilution is mandatory: 10 ml of sample made up to 300 ml, and the result multiplied by 30.

Why does potassium so often run short in aquaponics?

What dose of potassium bicarbonate should I use to raise the level?

Each gram of potassium bicarbonate provides 0.39 g of potassium, and it raises the KH at the same time:

Water volume	For an extra 10 mg/L of potassium	KH gained
100 L	2.6 g	0.7 °d
500 L	13 g	0.7 °d
1,000 L	26 g	0.7 °d

Dissolve the powder in a bucket of water from the system before pouring it in, then test again the next day.

What should you do if the level exceeds 30 mg/L?

Are the tubes and the measuring spoon included in the refill?

How should you handle a powder reagent classified as Danger?

Both bottles carry the hazard statement H314: causes severe skin burns and eye damage. If either splashes into your eye, rinse it straight away and keep rinsing for a long time, holding the eyelid open.

The powder needs a little more care than the liquid. Measure it out in a draught-free spot, over a sink, and never blow on the scoop to level it. Screw the child-resistant caps back on fully, store the box up high, somewhere dry and at room temperature, and take an empty bottle to the recycling centre with your household chemical waste.

Once you have read the result, empty the test tube down the sink: these reagents must never go into the water your fish live in.

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Reagent refill for potassium K test

The summary