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 measures the dissolved calcium and magnesium, in other words what your water provides to living things. It is read by titration, counting drops until the colour turns from red to green, in 2 minutes.

This value determines how strong a shrimp's carapace and a snail's shell will be, as well as part 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 multilingual instructions.
What you are measuring: dissolved calcium and magnesium, the two minerals on which moulting, shells and roots depend.
How to read the result: you count the drops until the colour changes from red to green. One drop equals 1 °dGH in 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 13-in-1 aquarium case and in the two pond cases.
What is sent to you: a parcel of 0.09 kg, with the reagent in its original box.

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

Total hardness is the sum of the dissolved calcium and magnesium. These are nutrients, taken up constantly by everything living in your water. A shrimp draws on calcium for its shell, a snail for its own shell, a plant takes up magnesium, and calcium helps a freshwater fish limit the loss of mineral salts through its gills.

🔀 GH and KH, two measurements

Confusing GH and KH is a common mistake, and it has a concrete consequence: a general hardness reading taken to stabilise the pH changes nothing about that pH, because general hardness counts calcium and magnesium; it is the carbonate hardness that counts carbonates, and it alone stabilises the pH. The two values have no fixed relationship: rainwater corrected with bicarbonate shows a decent KH and a GH close to zero, whereas reverse-osmosis water remineralised with carbonate-free salts shows the opposite. In practice, an unstable pH is a KH matter, and failed moults are a GH matter.

Check the bottle before counting the drops

The total hardness and carbonate hardness tests both use a 5 ml water sample and are read by counting drops, but their colour changes run in opposite directions: red to green here, blue to orange-yellow for KH. Rinse the test tube several times with the water being tested between the two measurements, and read the bottle label before you begin, because mistaking one reagent for the other gives a result that looks plausible and is wrong.

🦐 Shrimps and snails

Neocaridina, 6 to 10 °dGH

These are the red, orange and blue ones sold commercially. 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 grow in aquaponics or in a planted tank and the older leaves yellow between veins that stay green, also take the magnesium test: it shows whether it is that part that is lacking. Epsom salt then corrects it on its own, without affecting the calcium or the carbonates.

The maintenance ranges are read in German degrees, like the test result. Most freshwater fish and plants thrive 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 Lake Malawi and Lake Tanganyika cichlids between 5 and 20 °dGH. These are maintenance ranges, not danger thresholds.

🪨 The hardness of your water

The hardness of tap water depends on the geology, and the difference from one region to another can be tenfold: water that runs through granite terrain, as in Brittany, often comes out below 5 °f, whereas water from limestone terrain sometimes exceeds 40 °f, roughly 2.8 and 22 °dGH. Test your tap water before choosing your species, then pick those that thrive in that water rather than constantly correcting it.

🌧️ Rain, evaporation and GH

In a garden pond, the measured total hardness is often low, because rain dilutes the water with every shower. Summer has the opposite effect: the water evaporates, the minerals stay behind, and each top-up with mains water adds its own hardness to what remains in the pond. One reading in spring and another at the end of summer will show you which way your pond is heading, and the article on pond evaporation in summer explains how to compensate without shocking the water.

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 rule, recommended frequency, 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. The hardness ranges for shrimp come from specialist keeping guides.

Total hardness , in which kit?

Same manufacturer, same drop-based reagents. The 6-in-1 case covers the nitrogen cycle and pH; total hardness is found in this single test and in the 13-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	$59.00
13-in-1 water testing kit for aquariumsYour choice	12 parameters	13 tests	Yes	Yes	Yes	Yes	23 bottles	12	Yes	Yes	Yes	$138.00

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

13-in-1 water testing kit for aquariums

What you're measuring

Parameters covered (parameters)12 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

0.12 kg parcel, dispatched within 48 hours by Colissimo or Chronopost home delivery, to be chosen at checkout. The reagent ships in its original box. The exact 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