Box of the GH total hardness water test, 10.6 by 17.5 cm, drop-based test for aquarium and pond

Contents of the total hardness test: graduated plastic test tube from 5 to 20 ml, reagent bottle, syringe, and box

Reading the total hardness test: the reagent added drop by drop into the 5 ml test tube

Chart of recommended total hardness ranges, from 3 to 25 °dGH, for shrimps, fish and the pond

GH total hardness water test in drops

Name: GH total hardness water test in drops
Brand: JBL
Price: 12.0 USD
Availability: InStock

$12.00

$4.00 × 3 with no fees Klarna.

Total hardness accounts for dissolved calcium and magnesium — in other words, what your water contributes to living organisms. It is read by titration, counting the drops until the colour shifts from red to green, within 2 minutes.

This value determines the strength of a shrimp's shell, a snail's shell, and a share of a fish's mineral balance.

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The summary

What you receive: 1 bottle of GH reagent, 1 graduated plastic test tube, and the multilingual instruction leaflet.
What you measure: dissolved calcium and magnesium — the two minerals on which moulting, shell formation, and root development depend.
How to read the result: count the drops until the colour shifts from red to green. One drop equals 1 °dGH per 5 ml of water.
How long it takes: 2 minutes, with no waiting time. The colour change is immediate.
How to choose: total hardness is also included in the 14-in-1 aquarium kit and in both pond test kits.
What is sent to you: a parcel weighing 0.09 kg, reagent in its original box.

Drop-titration test, one drop equals 1 °dGH, calcium and magnesium combined

Total hardness combines dissolved calcium and magnesium. These are nutrients that everything living in your water draws on constantly. A shrimp uses the calcium for its shell, a snail for its shell, a plant its magnesium, and calcium helps a freshwater fish limit its mineral salt losses through the gills.

🔀 GH and KH, two measurements

Confusing GH and KH is a common mistake, and it has a real practical consequence: a total hardness reading taken to stabilise the pH has no effect on that pH at all, since total hardness measures calcium and magnesium; it is carbonate hardness that measures carbonates, and carbonate hardness alone that stabilises the pH. The two values have no fixed relationship: rainwater corrected with bicarbonate will show a correct KH and an almost zero GH, whereas osmosis water remineralised with carbonate-free salts will show the opposite. In practice, an unstable pH points to the KH, and failed moults point to the GH.

Check the bottle before counting the drops

Both the total hardness and carbonate hardness tests are carried out on 5 ml of water and read by counting the drops, but their colour changes go in opposite directions: red to green here, blue to orange-yellow for KH. Rinse the test tube several times with the water to be tested between the two measurements, and read the bottle label before you start, as using one reagent instead of the other gives a result that looks plausible but is wrong.

🦐 Shrimps and snails

Neocaridina, 6 to 10 °dGH

These are the standard red, orange and blue varieties. Below 5 °dGH the shell stays soft after moulting.

Caridina, 4 to 6 °dGH

These are the Crystal and Taiwan Bee varieties, almost always kept in remineralised osmosis water.

Moulting is the critical moment

A moult interrupted halfway through, the animal stuck in its shell, indicates water that is too poor.

Snails, the first visible sign

A shell that develops white pits and then crumbles at the top of the spire is a sign of water too low in calcium.

Separate magnesium from calcium using a second test

Total hardness adds calcium and magnesium together without separating them. If you are growing in aquaponics or in a planted bed and the older leaves are yellowing between veins that remain green, also run the magnesium test: it will tell you whether it is that element that is lacking. Epsom salt corrects it on its own, without affecting calcium or carbonates.

Maintenance ranges are expressed in German degrees, as are the test results. Most freshwater fish and plants do well between 8 and 25 °dGH, a lightly stocked planted tank is better kept between 3 and 10 °dGH, a garden pond between 6 and 20 °dGH, and Malawi and Tanganyika cichlids between 5 and 20 °dGH. These are maintenance ranges, not danger thresholds.

🪨 The hardness of your water

Tap water hardness depends on the local geology, and the variation from one region to another can be tenfold: water that runs through granite bedrock, as in Brittany, often comes out below 5 °f, whereas water from limestone areas sometimes exceeds 40 °f, roughly 2.8 and 22 °dGH respectively. Measure your tap water before choosing your species, then select those that thrive in it rather than constantly correcting it.

🌧️ Rain, evaporation and GH

In a garden pond, the total hardness reading is often low because rainfall dilutes the water with every shower. Summer produces the opposite effect: water evaporates, minerals remain, and each top-up from the mains supply adds its own hardness to what is already in the pond. A reading in spring and another at the end of summer will show you which direction your pond is moving, and the article on pond evaporation in summer explains how to compensate without causing shock.

Technical specifications

The essentials

Parameter measured: Total hardness, denoted GHCalcium and magnesium added together as a single value. The test does not separate them.
Measurement principle: Titration, counting dropsNo fixed range, no colour chart: you add the reagent until the colour change and count the drops
Value of one drop: 1 °dGH per 5 mlOver 10 ml, one drop equates to only 0.5 °dGH: this is how greater precision is achieved with soft water
Equivalences: 1.78 °fH, 1.25 °eThe French degree is used in drinking water analyses in France
Colour change: From red to greenThe opposite of the carbonate hardness test: mixing up the two reagents gives a plausible but incorrect result
Manufacturer's reference: JBL 2410800, PROAQUATEST rangeCode EAN 4014162241085

The procedure

Water volume: 5 mlMeasured in the graduated test tube supplied. It is this volume that determines the value of one drop
The steps: Rinse, fill, dose drop by drop, countSwirling after each drop
Waiting time: NoneThe colour change is immediate; there is no colour development time to observe
Total duration: Approximately 2 minutesThe harder the water, the more drops you need to count
Recommended frequency: 1 per day, then 1 per weekEvery day during the first week after filling, then as part of routine maintenance.
Environments covered: Freshwater and garden pondThis test is not suitable for saltwater

Security and parcels

Ranking: WarningThe lower of the two threshold levels under CLP regulations
Main risks: Flammable, causes skin and eye irritationH226, H315 and H319 statements
Precautions: Sink, well-ventilated room, out of reachChild-safety cap, keep away from all flames
Parcel weight: 0.09 kgPackaging included

To budget for separately

How to remineralise: A shrimp mineral salt, or Epsom saltThe first raises the total GH, the second raises only the magnesium fraction without affecting the carbonates
Reagent refill: Reagent only, ref. 2410900The graduated cylinder keeps well

10 further specifications are available in the detailed view.

In the box

1 bottle of GH reagent with child-safety cap
1 graduated plastic test tube from 5 to 20 ml
1 multilingual instruction leaflet, French included

Reference, EAN code, kit contents, protocol, reading guide, recommended frequency, and equivalences between degrees and hazard statements taken from the manufacturer's datasheet and instructions on 05/09/2026. The maintenance ranges come from the manufacturer and their UK retailers. The hardness ranges for shrimps come from specialist breeding guides.

Total hardness , in which kit?

Same manufacturer, same reagent drops. The 6-in-1 kit covers the nitrogen cycle and pH; total hardness is available in this test alone and in the 14-in-1.

A moulting shrimp needs calcium in the water Below 5 °dGH, moults fail and shells become pitted. Above 25 °dGH, most freshwater fish and plants are outside their maintenance range.

	Parameters covered (parameters)	Drop tests included (tests)	Total hardness GH	Carbonate hardness KH	pH, nitrites, nitrates and ammonium	Iron, phosphates, copper and oxygen	Reagent bottles (bottles)	Glass test tubes	Laboratory comparator block	Thermometer	Reagent refill sold separately	Price
Recommended Total hardness test onlyYour choice	1 parameters	1 tests	Yes	No	No	No	1 bottles	0	No	No	Yes	$12.00
6-in-1 Aquarium Water Testing KitYour choice	6 parameters	5 tests	No	Yes	Yes	No	9 bottles	3	Yes	No	Yes	$49.00
14-in-1 water analysis kit for aquariumYour choice	14 parameters	13 tests	Yes	Yes	Yes	Yes	23 bottles	12	Yes	Yes	Yes	$102.00

Total hardness test onlyRecommended

What you're measuring

Parameters covered (parameters)1 parameters

Drop tests included (tests)1 tests

Total hardness GHYes

Carbonate hardness KHNo

pH, nitrites, nitrates and ammoniumNo

Iron, phosphates, copper and oxygenNo

Equipment supplied

Reagent bottles (bottles)1 bottles

Glass test tubes0

Laboratory comparator blockNo

ThermometerNo

Budget

Reagent refill sold separatelyYes

6-in-1 Aquarium Water Testing Kit

What you're measuring

Parameters covered (parameters)6 parameters

Drop tests included (tests)5 tests

Total hardness GHNo

Carbonate hardness KHYes

pH, nitrites, nitrates and ammoniumYes

Iron, phosphates, copper and 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're measuring

Parameters covered (parameters)14 parameters

Drop tests included (tests)13 tests

Total hardness GHYes

Carbonate hardness KHYes

pH, nitrites, nitrates and ammoniumYes

Iron, phosphates, copper and 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 data sheets on 05/09/2026. A titration test uses neither a colour comparator block nor a glass measuring tube.

Documents & manuals

Official manufacturer's instructions, in French

Full four-step titration protocol, reference volume, equivalences between German, English and French degrees of hardness, and correction advice.

PDF · 1,5 Mo

Download

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delivery time

Package weight 0.12 kg, dispatched to a collection point or by Colissimo to your home address, your choice at checkout. The reagent is sent in its original box. The exact shipping cost is shown in the basket.

Frequently asked questions

6 questions

6 key questions

What GH do you need for shrimp?

I've raised my GH and my pH hasn't changed — why?

My RO water reads zero — what needs to be added?

First, decide on your target — it depends on what you are keeping.
Cut the RO water with tap water in the ratio this test gives you in 2 minutes.
Alternatively, add minerals separately using a remineralisation salt for shrimps.
Always retest: a dosage shown on a packet does not account for your starting water.

A hardness reading of zero indicates water that is completely free of calcium and magnesium, which must be remineralised before introducing any animals or plants.

My snails have eroded shells — is it the GH?

How do you get more accurate readings with very soft water?

In aquaponics, should you monitor GH?

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GH total hardness water test in drops

The summary