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

$7.00

Capacity	Price	Price per L	vs 30 ml
30 ml	$7.00	$233.33	—
60 ml	$8.00	$133.33	−43 %

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 against the colour chart on the bottle.
The range: from 4.0 to 8.5, which covers hydroponics, aquaponics, the pond and the aquarium.
How many tests: about 500 with the 30 ml bottle, more than 1,000 with the 60 ml one.
How fine the reading is: a colour chart of 7 shades, in half-point steps between pH 6.0 and 7.0.
What you receive: the bottle of reagent, its printed colour chart and a reading tube.
Format: 30 or 60 ml dropper bottle, dispatched by tracked parcel.

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

The pH drop test for growing water measures the pH of a nutrient solution, a pond or a tank, from 4.0 to 8.5, with no battery or calibration. Simply add 2 drops of reagent to the test tube and compare the colour with the 7-shade chart, in half-point steps between 6.0 and 7.0. The 30 ml bottle gives about 500 tests.

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 that a correctly dosed solution produces symptoms of deficiency. This drop test gives you the value in a minute, from pH 4.0 to 8.5, with no battery or calibration.

🎨 Reading a colour

The reagent is a colour indicator, whose shade changes with 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 colour obtained 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 grow room, where the lighting alters the perceived shade.

The range

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

Run time

The 30 ml bottle gives about 500 tests, the 60 ml one 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 range from pH 4.0 to 8.5, in steps 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 hydroponic target and most of the aquaponic one lie, the shades follow each other in half-point steps, which is enough to decide on a correction and then check its effect; below 6.0 and between 7.0 and 8.0, the gap between two shades is a full point, and the reading there mainly serves to spot clearly acidic or alkaline water. The test stays reliable over time, since it cannot drift out of calibration. The pocket electronic pH tester, on the other hand, gives you tenths 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 straight away 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 a grow light, because the pink of horticultural LEDs and the yellow of an old bulb alter the perceived shade. Keep the bottle closed and out of the sun, as a coloured indicator slowly degrades in light. If the shade of the reagent at rest has changed, do not try to interpret the reading; replace the bottle.

📅 How often to test

The frequency depends on the volume and the plant load more than on the type of crop. In a small, heavily planted reservoir, the value shifts within a day and a daily measurement is justified, whereas a large, lightly loaded volume is fine with 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 measurement after every addition of fertiliser, after every top-up of water and after a treatment, as these three actions are the ones that change the pH most noticeably.

Technical specifications

The measurement

Measurement range: pH 4.0 to 8.5It covers hydroponics, aquaponics, the pond and the freshwater aquarium.
Method: Colorimetric2 drops of indicator in the test tube filled halfway, then compare with the colour chart printed on the bottle.
Number of measures: approximately 500With the 30 ml bottle. The 60 ml bottle gives you 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, a whole point elsewhere.

Target values and reading conditions

Hydroponics: Target 5.8 to 6.2The range in which most mineral elements remain available to the plant.
Aquaponics: Target 6.8 to 7.0A compromise between the needs of the plants, those of the fish and those of the nitrifying bacteria.
Reading conditions: DaylightOn a white background. A pink horticultural light or a yellow lamp completely distorts the comparison.
Calibration: NoneThat is the advantage over electronics: no buffer solution, no probe to recalibrate.

Reagent and storage

Dose per test: 2 dropsAdded drop by drop from the cap, into the test tube filled halfway.
Storage: Closed bottle, kept away from lightRecap the bottle straight after measuring. A reagent whose colour at rest has changed can no longer be read.
Precautions: Keep out of reach of childrenDo not swallow, and rinse thoroughly with water in case of contact with the eyes.
Feed: NoneNo battery, no charger. The test works as it is.

To budget for separately

pH- corrector: Liquid pH-When the reading is above your target.
pH+ corrector: pH+ liquidWhen the reading is below your target.

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, with its colour chart printed on the label
1 reading test tube with its stopper

Measuring range, number of tests, 2-drop dose and contents: taken from the manufacturer's French page and the bottle label, checked on 11/10/2026.

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 electronic pH meter?

Both measure the same pH. They do not call for the same maintenance or the same attention.

A poorly calibrated pH meter displays a false reading without any warning An electronic meter gives you the tenth of a unit, provided it is properly maintained. One thing to know before you decide: with a brown or deeply coloured solution, reading by drops becomes difficult.

	Regular calibration required	Calibration solutions to buy again	Battery or rechargeable pack	Reading accurate to one decimal place	Can be measured on coloured water	Electronics prone to failure	Keeps for years without maintenance
Recommended Drop testYour choice	No	No	No	No	No	No	Yes
AMTRA Digital pH Tester ATC electronic pHYour choice	Yes	Yes	Yes	Yes	Yes	Yes	No

Drop testRecommended

In use

Regular calibration requiredNo

Calibration solutions to buy againNo

Battery or rechargeable packNo

Reading accurate to one decimal placeNo

Can be measured on coloured waterNo

Reliability

Electronics prone to failureNo

Keeps for years without maintenanceYes

AMTRA Digital pH Tester ATC electronic pH

In use

Regular calibration requiredYes

Calibration solutions to buy againYes

Battery or rechargeable packYes

Reading accurate to one decimal placeYes

Can be measured on coloured waterYes

Reliability

Electronics prone to failureYes

Keeps for years without maintenanceNo

Measuring range and number of measurements: product documentation. Features 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

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

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 to the plant. 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 of 6 would penalise the bacteria that convert ammonia. The article on pH regulation explains why the pH falls with nitrification and how to stabilise it.

What pH range does this test cover?

Drops or 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 everyday use, the drops to check that the probe has not drifted.

When two neighbouring shades leave you unsure, 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 exceeds what a colour comparison can give, and the electronic meter is justified.

How do you take an accurate measurement?

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