30 ml reagent bottle and its reading tube

60 ml reagent bottle and its reading tube

Colour chart on the back of the bottle, from pH 4.0 to 8.5

60 ml bottle and test tube side by side, current packaging

Former packaging of the same reagent, still in circulation

Bottle and test tube placed at the base of a plant, in-context shot

Drop pH test for growing water

$6.85

Contenance	Prix	Prix au L	vs 30 ml
30 ml	$6.85	$228.33	—
60 ml	$8.71	$145.17	−36 %

The pH drop test measures the pH of a nutrient solution, a pond, or a tank, over a range of 4.0 to 8.5. A few drops of reagent in a water sample, a colour to compare against the chart, and the reading is done.

The test requires no battery, no probe, and no calibration. The 30 ml bottle gives approximately 500 measurements.

Contenance : 30 ml

30 ml

60 ml

7/7 customer service by e-mail

Payment in instalments, free of charge

The summary

What it is: a colorimetric pH test — a few drops of reagent in a water sample and a colour to compare against a reference chart.
The range: 4.0 to 8.5, covering hydroponics, aquaponics, ponds, and aquariums.
How many tests: around 500 with the 30 ml bottle, double that with the 60 ml.
Reading accuracy: half a pH unit — enough to decide on a correction and then verify it.
To use alongside: a dedicated transparent glass for sampling, and a pH- or pH+ adjuster to act on what you read.
Format: dropper bottle of 30 or 60 ml, dispatched with tracked delivery.

Colorimetric pH test, range 4.0 to 8.5, approximately 500 readings per 30 ml bottle

Measuring pH is not a refinement, outside its range, a perfectly dosed nutrient solution becomes unusable, as the elements it contains lock up in a form that cannot be absorbed. The symptoms look for all the world like a deficiency, and you end up adding fertiliser to water that has no shortage of it.

🎨 Reading a colour

The range

The test measures from 4.0 to 8.5. This range covers soilless cultivation, around 6, aquaponics, around 7, and ponds.

The autonomy

It yields around 500 tests from the 30 ml bottle. At two tests per week, that will last you years.

Nothing to maintain

It requires no battery, no calibration, no buffer solution and no probe to keep moist.

Its limit

The visual comparison gives you the half-point, not the hundredth of a point.

🔬 Reading precision

A colour indicator changes shade according to the acidity of the medium. You take a sample, add a few drops of reagent, shake it, then compare the resulting colour with the printed chart. The reading is done by eye, in daylight and against a white background. A yellow lamp or a pink horticultural light will skew your reading, and that is by far the most common cause of incorrect results with this type of test. Take your sample near a window, or bring it out of the growing room before reading it.

The drop test is reliable over time, since it doesn't drift out of calibration, doesn't break down, and won't be affected by a probe accidentally left to dry out. It is, however, slow when you're measuring several times a day. A electronic pH meter gives you a reading to one decimal place in two seconds, in exchange for regular calibration. Many growers keep both: the electronic meter for daily use, and the drops to cross-check it.

Your target depends on the crop

Your target depends on what you are growing. In hydroponics, aim for 5.8 to 6.2. In aquaponics, aim for 6.8 to 7.0. Pick up a correction product at the same time, a pH- adjuster or a pH+ adjuster, along with a small transparent container kept solely for taking samples. Our article on pH regulation covers the targets in detail.

Light and storage

Never read the colour under grow lighting, as the pink of horticultural LEDs and the yellow of an old incandescent bulb will shift the shade. Keep the bottle sealed and away from sunlight, a colour indicator degrades slowly when exposed to light. If the resting colour of the reagent has changed, do not try to interpret the reading; replace the bottle.

📅 How often to measure

The frequency depends more on tank volume and plant load than on the type of culture. In a small, heavily planted reservoir the value can shift within a day, making daily measurement worthwhile, whereas a large, lightly loaded volume needs only two readings a week. Always measure at the same time of day, as the pH of a solution varies with plant uptake and temperature. Take a reading systematically after every fertiliser addition, every top-up of water, and every treatment, these three actions being the ones that shift the value most noticeably.

Technical specifications

The measurement

Measurement range: pH 4.0 to 8.5It covers hydroponics, aquaponics, the pond and the freshwater aquarium.
Method: ColorimetricA few drops of indicator into a sample, then comparison of the colour against a printed chart.
Number of readings: around 500With the 30 ml bottle. The 60 ml bottle gives approximately twice as many doses.
Reading precision: The half pH pointTwo adjacent shades on the chart can be distinguished to half a point — which is exactly what is needed to decide on a correction.

Target values by crop

Hydroponics: Target 5,8 to 6,2Range within which most mineral elements remain available to the plant.
Aquaponics: Target 6.8 to 7.0A balance between the needs of the plants, the fish, and the nitrifying bacteria.
Reading conditions: Natural daylightAgainst a white background. Pink horticultural lighting or a yellow lamp will completely distort the comparison.
Calibration: NoneThat is the advantage over electronic testing: no buffer solution, no probe, no drift to correct.

Reagent and storage

Reagent form: Liquid colour indicatorA few drops per measure, dispensed using the dropper built into the cap.
Storage: Sealed, away from lightReplace the cap immediately after measuring and store the bottle with its colour chart. A reagent whose resting colour has changed can no longer be read accurately.
Precautions: Out of reach of childrenDo not ingest, and rinse thoroughly with water if contact with the eyes occurs.
Power supply: NoneNo battery, no charger. The test works straight out of the box.

To budget for separately

Sampling container: A clean transparent glassReserved for this purpose only and rinsed with clean water. Any residue of soap or fertiliser will skew the reading.
pH corrector: pH- or pH+Depending on the direction of correction: pH- if you are too high, pH+ if you are too low.

6 further specifications are available in the detailed view.

In the box

1 dropper bottle of reagent, in the chosen size: 30 ml or 60 ml.
1 colour comparison chart.

Measurement range, number of tests from the 30 ml bottle and kit contents: product documentation. The number of tests from the 60 ml bottle follows its volume. Values recorded on 10 September 2026.

Drops or electronic pH meter?

Both measure the same pH. They do not require the same maintenance or the same level of attention.

A poorly calibrated pH meter lies more than a bottle of drops The electronic meter reads to one decimal place, provided it is properly maintained. One point to be aware of before deciding: on a dark or heavily coloured solution, the drop-count reading becomes difficult.

	Regular calibration required	Calibration solutions to restock	Battery or rechargeable cell	Numerical reading to one decimal place	Measurement possible on coloured water	Breaks down	Stores for years without any maintenance
Recommended Drop testYour choice	No	No	No	No	No	No	Yes
Electronic pH meterYour choice	Yes	Yes	Yes	Yes	Yes	Yes	No

Drop testRecommended

In use

Regular calibration requiredNo

Calibration solutions to restockNo

Battery or rechargeable cellNo

Numerical reading to one decimal placeNo

Measurement possible on coloured waterNo

Reliability

Breaks downNo

Stores for years without any maintenanceYes

Electronic pH meter

In use

Regular calibration requiredYes

Calibration solutions to restockYes

Battery or rechargeable cellYes

Numerical reading to one decimal placeYes

Measurement possible on coloured waterYes

Reliability

Breaks downYes

Stores for years without any maintenanceNo

Measurement range and number of tests: product documentation. Specifications of the electronic pH meter: data sheet for the model sold in the shop. Values recorded on 10 September 2026.

Documents & manuals

Manufacturer's page, pH test

Presentation of the test by Terra Aquatica, in English, with the measurement range and the number of tests stated.

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delivery time

A lightweight, non-fragile bottle, dispatched by tracked parcel from France. It fits into any order without affecting the shipping rate. Exact costs and final delivery times are displayed at checkout once your address has been entered. Outside the European Union, import duties and taxes remain the responsibility of the recipient. Delivery times run from the date of dispatch, excluding public holidays.

Frequently asked questions

6 questions

6 key questions

What pH should I aim for in my system?

In hydroponics, aim for 5.8 to 6.2 — the range in which mineral elements remain available for uptake. In aquaponics, aim for 6.8 to 7.0, a compromise between plants, fish, and nitrifying bacteria.

The two targets differ because the constraints do: in aquaponics, dropping to 6 would penalise the bacteria that convert ammonia. Our article on pH regulation covers this trade-off in detail.

What pH range does this test cover?

Drops or electronic pH meter?

Aspect	Drop test kit	pH meter
Accuracy	to 0.5	to 0.1
Long-term reliability	excellent	drifts, needs calibration
Maintenance	none	probe and calibration solutions
Speed	one minute	two seconds
Power supply	none	battery

Many growers keep both: the electronic meter for daily use, the drops to check that the probe has not drifted.

When two similar shades leave you unsure, place the sample against a white sheet, check it in daylight, then repeat the test with a fresh sample. If you hesitate every single time, your need for precision goes beyond what a colour comparison can provide, and an electronic meter is the right choice.

How do you take a correct reading?

Which size to choose, 30 or 60 ml?

Can it be used in a fish tank?

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Drop pH test for growing water

The summary