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

$10.00

Capacity	Price	Price per L	vs 30 ml
30 ml	$10.00	$333.33	—
60 ml	$12.00	$200.00	−40 %

The liquid drop pH test measures the pH of a nutrient solution, a pond or a tank, across a range of 4.0 to 8.5. Add 2 drops of reagent to the test tube filled halfway, then compare the colour you get with the colour chart printed on the bottle.

The test works without batteries, a probe or calibration. The 30 ml bottle gives about 500 tests, and the 60 ml bottle more than 1,000.

Ref. TA-PHTK-30·Water test

Capacity : 30 ml

30 ml

60 ml

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The summary

What it is: a colorimetric pH test, where 2 drops of reagent added to the test tube give a colour to compare with the chart on the bottle.
The range: from 4.0 to 8.5, which covers hydroponics, aquaponics, ponds and aquariums.
How many tests: around 500 with the 30 ml bottle, more than 1,000 with the 60 ml one.
Reading precision: a colour chart with 7 shades, in half-point steps between pH 6.0 and 7.0.
What you receive: the reagent bottle, its printed colour chart and a test tube for reading.
Precautions: the reagent is harmful if swallowed; the sample is discarded after reading, never into the fish water.

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

This drop test measures pH from 4.0 to 8.5 with no battery and no calibration, for a nutrient solution, a pond or an aquaponic system, with about 500 measurements per 30 ml bottle. The reagent contains methanol: it stays in the test tube, never in the fish water. The 60 ml bottle doubles the supply.

The pH of a nutrient solution determines the form in which the mineral elements are present: outside the suitable range, iron, phosphorus or manganese precipitate or remain in a form the roots can no longer absorb, so a correctly dosed solution can still produce deficiency symptoms. This drop test gives you the value in one minute, from pH 4.0 to 8.5, with no battery and no calibration.

🎨 Reading a colour

The reagent is a colour indicator, whose shade changes according to the acidity of the water. Fill the test tube supplied halfway with the water to be tested, add 2 drops of reagent, close the tube and shake it gently, then compare the resulting colour with the colour chart printed on the bottle label. The reading is made by eye, in daylight and against a white background, near a window rather than in the growing room, whose lighting alters the perceived shade.

The range

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

Run time

The 30 ml bottle gives about 500 tests, the 60 ml bottle more than 1,000. At 2 tests a week, the small bottle lasts for years.

No maintenance needed

The test needs no battery, no calibration, no buffer solution and no probe to keep moist.

The colour chart

Its 7 shades run from pH 4.0 to 8.5, with a step of 0.5 between 6.0 and 7.0, where most growing targets lie.

🔬 Reading precision

The colour chart has 7 shades: pH 4.0, 5.0, 6.0, 6.5, 7.0, 8.0 and 8.5. Between 6.0 and 7.0, where the target for hydroponics and most of the target for aquaponics lie, the shades follow each other in half-point steps, which is enough to decide on a correction and then to check its effect; below 6.0 and between 7.0 and 8.0, the gap between two shades is a whole point, and the reading there serves mainly to spot clearly acidic or alkaline water. The test stays reliable over time, since it never drifts out of calibration. The pocket electronic pH tester, on the other hand, gives you the tenth of a point in a few seconds, in exchange for regular calibration, and many growers keep both: the electronic one for everyday use, the drops to check the probe.

Keep a pH corrector close to the bottle

Measuring is only worthwhile if you can act at once on the value you read. In hydroponics, the target lies between 5.8 and 6.2; in aquaponics, between 6.4 and 7.5. The pH- corrector lowers the pH of a solution that is too alkaline, the pH+ corrector raises that of water that is too acidic, and the test then lets you check the effect of the dose. The article on pH regulation details the method of correcting with small, regular additions.

Light and storage

Never read the colour under grow lighting, as the pink of horticultural LEDs and the yellow of an old bulb alter the perceived shade. Keep the bottle closed and out of direct sunlight, as a colour indicator slowly degrades in light. If the colour of the reagent at rest has changed, do not try to interpret the measurement; replace the bottle.

📅 How often to measure

The frequency depends on the volume and the plant load more than on the type of crop. In a small, heavily planted sump tank, the value shifts within a day and a daily measurement is justified, whereas a large, lightly loaded volume needs only two readings a week. Always measure at the same time of day, because the pH of a solution varies with plant uptake and temperature. Finally, always take a fresh reading after each addition of fertiliser, after each top-up of water and after a treatment, as these three actions are the ones that change the pH most markedly.

🧪 A reagent to keep in the test tube

The colour indicator is dissolved in a mixture containing 5 to 10% methanol. The bottle therefore carries the Warning label: it is harmful if swallowed, and significant exposure may affect certain organs. In practice, this changes nothing about the procedure, provided you follow it: you fill the test tube halfway with the sampled water, add 2 drops, read the colour, then discard the sample and rinse the tube. In an aquaponic system, where you are aiming for a pH of 6.4 to 7.5, the reagent must never reach the fish water, which then irrigates your crops. Wash your hands after the measurement, and store the bottle closed, upright, out of reach of children, next to the pH- corrector that will be used to correct the value read.

Technical specifications

The measurement

Measuring range: pH 4.0 to 8.5It covers hydroponics, aquaponics, the pond and the freshwater aquarium.
Method: Colorimetric2 drops of indicator in the half-filled test tube, then compare with the colour chart printed on the bottle.
Number of tests: around 500With the 30 ml bottle. The 60 ml bottle gives more than 1,000.
Colour chart: 7 shades, from 4.0 to 8.5Steps of 0.5 between 6.0 and 7.0 and between 8.0 and 8.5, and of a whole point elsewhere.

Target values and reading conditions

Hydroponics: Target 5.8 to 6.2Range in which most mineral elements remain available to the plant.
Aquaponics: Target 6.4 to 7.5An aquaponic benchmark, a compromise between plants, fish and bacteria; the FAO guide recommends 6 to 7
Reading conditions: DaylightAgainst a white background. Pink horticultural lighting or a yellow lamp completely distorts the comparison.
Calibration: NoneThat is the advantage over electronic testing: no buffer solution, no probe to recalibrate.

Hazard labelling

Signal word: WarningThe reagent contains 5 to 10% methanol
Pictograms: Exclamation mark and health hazardGHS07 for oral toxicity, GHS08 for organ damage
Hazard statements: H302, H371Harmful if swallowed, suspected of causing serious damage to organs
Precautionary statements: P101, P102, P264, P308+P311, P405Label to show the doctor, out of reach of children, hands washed after use, poison centre if exposed, bottle stored under lock and key
Storage: Keep the bottle closed and away from lightRecap the bottle immediately after measuring. A reagent whose resting colour has changed can no longer be read.
Precautions: Keep out of reach of childrenSample discarded after reading, never poured back into the tank; rinse eyes with water in case of contact

To allow for in addition

pH- adjuster: Liquid pH-When the value you read is above your target.
pH+ adjuster: Liquid pH+When the value you read is below your target.

8 further specifications are available in the detailed view.

In the box

1 dropper bottle of reagent, in your chosen size, 30 ml or 60 ml, with its colour chart printed on the label
1 reading test tube with its cap

Manufacturer's values (French page, bottle label and 2024 safety data sheet). Growing targets: aquaponic benchmarks, including the FAO guide.

Manufacturer and product safety

Manufacturer: TERRA AQUATICA (SAS, SIREN 840329619), ex General Hydroponics Europe
Postal address: 4 boulevard du Biopole, ZI du Biopole, 32500 Fleurance, France
Contact: info@terraaquatica.com ; +33 5 62 06 08 30
Website: www.terraaquatica.com

Information provided under Regulation (EU) 2023/988 on general product safety.

Drops or an electronic pH meter?

Both measure the same pH. They do not require the same upkeep or the same attention.

A poorly calibrated pH meter shows a false value without warning you Electronics give you the tenth, provided they are properly maintained. One thing to know before you decide: on a brown or heavily coloured solution, reading by drops becomes difficult.

	Regular calibration required	Calibration solutions to buy again	Cell or battery	Numerical reading to the tenth	Can be measured in tinted water	Electronics prone to failure	Keeps for years without maintenance
Recommended Drop testYour choice	No	No	No	No	No	No	Yes
Pocket electronic pH tester, accurate to the hundredthYour choice	Yes	Yes	Yes	Yes	Yes	Yes	No

Drop testRecommended

In use

Regular calibration requiredNo

Calibration solutions to buy againNo

Cell or batteryNo

Numerical reading to the tenthNo

Can be measured in tinted waterNo

Reliability

Electronics prone to failureNo

Keeps for years without maintenanceYes

Pocket electronic pH tester, accurate to the hundredth

In use

Regular calibration requiredYes

Calibration solutions to buy againYes

Cell or batteryYes

Numerical reading to the tenthYes

Can be measured in tinted waterYes

Reliability

Electronics prone to failureYes

Keeps for years without maintenanceNo

Range and number of tests for the drop test, characteristics of the electronic tester taken from its data sheet.

Documents & manuals

Safety data sheet for the reagent, in French

Composition, hazard statements, first aid, storage and disposal of the pH reagent, 2024 version.

PDF · 169 Ko

Download

Estimate your
delivery time

Light, non-fragile bottle, dispatched by tracked parcel from France. It slips into any order without changing the shipping cost. The exact charges and final delivery times are shown in your basket once the address has been entered. Outside the European Union, import duties and taxes are payable by the recipient. Delivery times run from the date of dispatch, excluding public holidays. 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

Which pH should I aim for in my system?

In hydroponics, aim for 5.8 to 6.2, the range in which mineral nutrients remain available to the plants. In aquaponics, aim for 6.4 to 7.5, a compromise between plants, fish and nitrifying bacteria.

The two targets differ because the constraints differ: in aquaponics, a pH that falls below 6 penalises the bacteria that convert ammonia. The article on pH regulation explains why pH falls with nitrification and how to stabilise it.

What pH range does this test cover?

Drops or an electronic pH meter?

Point	Drop test	pH meter
Resolution	0.5 to 1 point	a tenth
Reliability over time	excellent	regular calibration
Maintenance	none	probe and solutions
Speed	one minute	a few 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 neighbouring shades leave you hesitating, place the sample on a white sheet of paper, read it again in daylight, then repeat the measurement on a fresh sample. If the doubt returns every time, your need for precision goes beyond what a colour comparison can give, and the electronic meter is justified.

How do I take an accurate measurement?

Which size should you choose, 30 or 60 ml?

Does the reagent pose a risk to my fish?

None if it stays in the test tube, and it must never leave it. The reagent contains methanol, which is harmful if swallowed: the measurement is made on a sample taken from the water, never in the tank itself, and the coloured sample is discarded after reading rather than poured back.

You can therefore monitor the pH of a pond, an aquarium or an aquaponic system with confidence, provided the reagent never touches the water the fish live in.

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Drop pH test for growing water

The summary