Cardboard box for the iron Fe drop test, labelled 50 tests, for aquarium, pond and saltwater

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

Colour chart for the iron test placed under the comparator block and its two test tubes, nine colour fields from 0.02 to 1.5 mg per litre

Adding the five drops of reagent to the test tube placed in the comparator block, above the colour chart

Drop-bottle of iron Fe reagent, white cap, alone on a white background

Iron Fe water test in drops

Name: Iron Fe water test in drops
Brand: JBL
Price: 16.5 EUR
Availability: InStock

16,50 €

Iron is one of the first elements to run short in an aquaponic system, and a deficiency shows clearly on the foliage. This test measures truly dissolved iron, from 0.02 to 1.5 mg/L, in twelve minutes.

The test is for checking a supplement rather than carrying out weekly rounds: measure before, measure after, and find out exactly what your system is consuming.

7/7 customer service by e-mail

Payment in instalments, free of charge

The summary

What you receive: one reagent bottle, two glass test tubes, a syringe, a grey comparator block and the colour chart, for approximately 50 tests.
What you read: dissolved iron, from 0.02 to 1.5 mg/L, across nine colour fields, in freshwater, pond water and saltwater.
Target levels: 0.1 to 0.2 mg/L in planted water, and no more than 0.05 mg/L in saltwater.
When to test: just before dosing, then one to two days afterwards. Two readings tell you your actual consumption.
How to choose: iron is included in the 14-in-1 kit, not the 6-in-1.
What gets sent to you: a parcel weighing 0.12 kg, with the bottle and glassware secured in the original box.

Drop test for dissolved iron, from 0.02 to 1.5 mg/L, for managing chelate dosing

In aquaponics, fish feed provides very little iron, making it the most common deficiency in grow beds. It shows up visually well before it can be measured, provided you look at the right part of the plant, as three other deficiencies produce a similar yellowing of the foliage. This test measures the iron actually dissolved in your system's water and allows you to draw a firm conclusion.

🍃 Where the yellowing starts

Iron is one of the least mobile elements within a plant. Once fixed in a leaf, it is no longer redistributed to younger organs, so the deficiency appears on the uppermost leaves, where the blade turns pale between veins that remain green. The oldest leaves lower down the stem may meanwhile stay perfectly green for several weeks. By contrast, nitrogen and magnesium travel through the sap and are drawn back towards new growth, so their deficiency starts at the bottom of the plant. Observing where the yellowing begins therefore remains the only reliable first step before any testing, and the guide on iron deficiency in aquaponics covers this species by species.

🧲 Precipitation and chelate form

There remains a chemical constraint that governs the choice of product. In aerated water, unchelated iron does not stay in solution; above pH 6.5, it oxidises and precipitates within a few hours. An aquaponic system combines precisely these two conditions, since it brings together heavily oxygenated water and a pH that most often stays above 6.5. A zero reading taken the day after dosing therefore indicates precipitation rather than plant uptake, and telling the two apart completely changes how you should respond. This is why iron is sold in chelated form, with a complexing molecule keeping it dissolved; and since each chelating agent has a pH threshold beyond which it releases the iron, the form you choose should be based on the pH of your water rather than on the measured iron level.

EDTA 13 %

Lowest pH threshold. Reserved for acidic water, it releases iron as soon as pH rises.

DTPA 11 %

The standard compromise, stable up to neutral to slightly alkaline water.

EDDHA 6 %

Upper pH limit, for hard water. It turns the water red.

Preliminary measurement

Measure your water's pH before buying the chelate, as it is the pH that determines the correct form.

The ammonium reagent skews the iron reading

A trace of ammonium test reagent left in a test tube will push the iron reading upward, and this is by far the most common cause of an abnormally high result. Rinse your test tubes three times with the water you are testing before each measurement, and avoid using the same glassware for both tests without that rinse. Dedicated glassware for each parameter remains the safest approach once you are monitoring several values.

Choose the chelate form before the dose

pH determines whether an iron supplement will remain available or precipitate, making it the measurement to take before you even place your order. The liquid pH test can be carried out on the same water sample. Above pH 7, the EDDHA 6% chelate remains stable where an EDTA has already released its iron, whereas between 6 and 7, DTPA 11% is sufficient and does not colour the water. Choosing the right form based on pH, rather than picking one at random off the shelf, means you avoid repeated applications with no visible improvement in the foliage.

🧪 Bracket a dosing with two measurements

Unlike nitrates, whose concentration rises on its own as long as the fish are being fed, the iron content depends entirely on what you add. It rises after each addition, then falls as plants absorb it and a portion precipitates. A single measurement therefore tells you little, whereas by bracketing each addition with two readings, one just before and another 24 to 48 hours after, you can directly gauge how much iron remained available. The rate at which the value declines over the following days then tells you the interval to observe between additions. Both of these markers depend on the pH of your water, the area under cultivation, and the species in place, which means that no general dosing guideline can replace them.

🌿 When iron levels are sufficient

A correct reading is just as useful as a low one, since it rules out iron as the cause and directs you elsewhere. Two causes tend to dominate when the level is adequate yet young leaves remain pale. A high pH blocks uptake long before the element disappears from the water, and a manganese deficiency produces a very similar leaf pattern. If the yellowing starts at the bottom of the plant instead, the tests to run are for magnesium or potassium, and the guide to deficiencies in aquaponics presents these patterns side by side.

Technical specifications

The essentials

Parameter measured: Dissolved iron, in mg/LThe reaction colours the iron remaining in solution; anything that has precipitated to the bottom of the tank is not counted.
Colour chart range: 0.02 to 1.5 mg/LFirst field reading below 0.02, last field 1.5
The colour fields: 0,02 · 0,05 · 0,1 · 0,2 · 0,4 · 0,6 · 0,8 · 1,0 · 1,5Nine steps, closely spaced at the lower end of the scale where the decision to dose is made
Target values: 0.1 to 0.2 mg/L in planted waterUp to 0,05 mg/L only in marine water. A heavily planted tank can tolerate up to 0,6 mg/L.
Tests per kit: Around 50A single reagent bottle to use up — the most economical in the range
Manufacturer reference: JBL 2411600, PROAQUATEST rangeEAN code 4014162241160. Not to be confused with the refill, reference 2411700

The procedure

Sample volume: 2 times 5 mlOne test tube receives the reagent; the other is left as it is and serves as a control.
The steps: Rinse, collect, dose, mix, wait, readFive drops from a single bottle, held vertically, tip dry and bubble-free
Rest time: 10 minutesAllow full colour development. Reading too early will underestimate the value.
Total duration: Approximately 12 minutesRinsing and reading included
Reading: In the notch of the comparator blockThe block is slid along the colour chart until the two shades match
Pitfall to know about: Rinse beforehand, several timesTraces of ammonium reagent in the test tube will give a falsely high iron reading.

Security and parcels

Ranking: WarningThe lower of the two CLP regulation thresholds
Main risks: Harmful if swallowed, skin allergy riskHazard statements H302, H317, and H319. Wear gloves if your skin is sensitive.
Storage: In a dry place, at room temperatureIn the original packaging, away from direct light.
Parcel weight: 0,12 kgPackaging included

To budget for separately

Iron to dose: A chelate suited to your pHEDTA in acidic water, DTPA in neutral water, EDDHA in hard water
Reagent refill: Reagent only, ref. 2411700The glassware, the comparator block and the colour chart keep well

10 further specifications are available in the detailed view.

In the box

1 dropper bottle of Fe reagent
2 glass test tubes with screw caps
1 graduated syringe for drawing 5 ml
1 grey comparator block with two chambers
1 colour chart with nine fields, from 0.02 to 1.5 mg/L
1 multilingual instruction leaflet with the protocol in French

Reference, EAN code, number of tests, kit contents, protocol, interference with the ammonium reagent and hazard statements recorded from the manufacturer's data sheet and instructions on 05/09/2026. The range and the nine increments are taken from a photograph of the colour chart supplied.

The iron test on its own, or a kit that includes it

Iron is included in the 14-in-1 kit but not in the 6-in-1.

Chlorosis always starts with the young leaves Iron does not travel freely within the plant: the deficiency strikes new growth and leaves the veins green. If your older leaves are yellowing, nitrogen is more likely to be the cause.

	Parameters covered (parameters)	Drop tests included (tests)	Fer Fe	pH, KH, nitrites and nitrates	GH, phosphates, copper, silicates, oxygen	Reagent bottles (bottles)	Glass test tubes	Laboratory comparator block	Thermometer	Reagent refill sold separately	Price
Recommended Iron test onlyYour choice	1 parameters	1 tests	Yes	No	No	1 bottles	2	Yes	No	Yes	16,50 €
6-in-1 Aquarium Water Testing KitYour choice	6 parameters	5 tests	No	Yes	No	9 bottles	3	Yes	No	Yes	42,50 €
14-in-1 water analysis kit for aquariumYour choice	14 parameters	13 tests	Yes	Yes	Yes	23 bottles	12	Yes	Yes	Yes	88,90 €

Iron test onlyRecommended

What you are measuring

Parameters covered (parameters)1 parameters

Drop tests included (tests)1 tests

Fer FeYes

pH, KH, nitrites and nitratesNo

GH, phosphates, copper, silicates, oxygenNo

Equipment supplied

Reagent bottles (bottles)1 bottles

Glass test tubes2

Laboratory comparator blockYes

ThermometerNo

Budget

Reagent refill sold separatelyYes

6-in-1 Aquarium Water Testing Kit

What you are measuring

Parameters covered (parameters)6 parameters

Drop tests included (tests)5 tests

Fer FeNo

pH, KH, nitrites and nitratesYes

GH, phosphates, copper, silicates, oxygenNo

Equipment supplied

Reagent bottles (bottles)9 bottles

Glass test tubes3

Laboratory comparator blockYes

ThermometerNo

Budget

Reagent refill sold separatelyYes

14-in-1 water analysis kit for aquarium

What you are measuring

Parameters covered (parameters)14 parameters

Drop tests included (tests)13 tests

Fer FeYes

pH, KH, nitrites and nitratesYes

GH, 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 recorded from the three product sheets on 05/09/2026.

Documents & manuals

Official manufacturer's instructions, French section

The full six-step protocol, the reference volume of 2 × 5 ml, the five drops of reagent, the ten minutes' rest, and the warning about sharing test tubes with the ammonium test.

PDF · 2,9 Mo

Download

Estimate your
delivery time

Parcel weighing 0.12 kg, dispatched to a collection point or by Colissimo to your home address, as chosen at checkout. The reagent bottle is sent in its original cardboard box, with the glassware securely packed. The exact shipping cost is shown in the basket.

Frequently asked questions

8 questions

6 key questions, 8 in the detailed view

What iron level should you aim for in the water?

My test reads 0 straight after dosing — is that normal?

Yes, and this is in fact the most common scenario. Bare iron oxidises and precipitates within a few hours as soon as the pH exceeds 6.5 in well-oxygenated water. A zero reading the following day does not mean your plants have consumed everything — it means the iron is no longer in solution.

This is the whole purpose of chelates: the molecule surrounding the iron keeps it dissolved, and each chelating agent has a pH ceiling beyond which it releases its hold. If your zero readings persist despite a chelated dose, it is the form of the chelate that needs changing, not the quantity.

Why do two iron tests give different readings?

The colour doesn't match any box on the colour chart — what went wrong?

Should you measure pH as well as iron?

Can I use the test tube from another test of the same brand?

How often should you take measurements?

Can the reagent trigger a skin allergy?

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Iron Fe water test in drops

The summary