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 water test, total hardness, drop-based

Name: GH water test, total hardness, drop-based
Brand: JBL
Price: 1200.0 RSD
Availability: InStock

1,200.00 RSD

400.00 RSD × 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.

Water test

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The summary

What you receive: 1 bottle of GH reagent, 1 graduated plastic test tube and multilingual instructions.
What you measure: 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.
Duration: 2 minutes, with no waiting. The colour change is immediate.
How to choose: total hardness is also included in the 13-in-1 case for aquariums and in the two cases for ponds.
The GH reagent: flammable and irritant, it is used on a 5 ml sample and never touches the fish water.

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

This test measures total hardness, the dissolved calcium and magnesium, by counting drops until the colour changes from red to green: one drop equals 1 °dGH on 5 ml. It suits shrimp, snails and aquaponics. The reagent stays in the test tube, never in the fish water, and can be bought on its own.

Total hardness is the sum of the dissolved calcium and magnesium. These are nutrients, constantly drawn on by everything living in your water. A shrimp takes the calcium for its shell from it, a snail the calcium for its own, a plant its 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 total hardness reading taken to stabilise the pH changes nothing about that pH, because total hardness counts calcium and magnesium; it is the carbonate hardness that counts the carbonates, and it alone stabilises the pH. The two values have no fixed relationship: rainwater corrected with bicarbonate shows a good KH and an almost nil GH, whereas reverse-osmosis water remineralised with carbonate-free salts shows the opposite. In practice, an unstable pH is therefore a KH matter, and failed moults are a GH matter.

Check the bottle before counting the drops

The total hardness and carbonate hardness tests are both carried out on 5 ml of water and read by counting drops, but their colour changes run in opposite directions: from red to green here, from 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 starting, because a reagent mistaken for the other gives a result that is plausible and wrong.

🦐 Shrimp and snails

Neocaridina, 6 to 10 °dGH

These are the red, orange and blue ones sold in shops. Below 5 °dGH the shell stays soft after moulting.

Caridina, 4 to 6 °dGH

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

Moulting is the critical moment

A moult interrupted halfway, with the animal stuck in its shell, is a sign of water that is too poor.

Snails, the first visible sign

A shell that becomes pitted with white holes and then crumbles at the top of the spire signals water that is too low in calcium.

Separate the magnesium from the calcium with 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 turn yellow between veins that stay green, also take the magnesium test: it shows whether it is this 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.

🪨 Your water hardness

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

🌧️ Rain, evaporation and GH

In a garden pond, the total hardness measured 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 is already 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 causing a shock.

🧴 An alcohol-based reagent

The GH reagent is a solution of triethanolamine and ethanol, with a little ammonia and EDTA: it is flammable and irritates the skin and eyes. Count your drops over a sink, away from any flame, holding the test tube at arm's length, and recap the bottle between measurements so the alcohol does not evaporate, which would also skew the titration. The water that has turned green then goes down the sink, never into the tank: in aquaponics, this water irrigates your crops after passing through the fish. The number of measurements you get from the bottle depends on the hardness of your water, since each degree uses one drop, and the GH reagent refill fits in the same case.

Technical specifications

Measuring total hardness

Parameter measured: Total hardness, denoted GHCalcium and magnesium added together into a single value. The test does not separate them
Measuring principle: Titration, counting the dropsNo colour chart: you count the drops until it turns green
Value of one drop: 1 °dGH per 5 mlIn 10 ml, one drop is worth only 0.5 °dGH: this is how you gain precision in soft water
Equivalences: 1.78 °fH, 1.25 °eThe French degree is the one 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 result that is plausible and wrong
Manufacturer's reference: JBL 2410800, PROAQUATEST rangeEAN code 4014162241085

The procedure

Water volume: 5 mlMeasured in the graduated test tube supplied. It is this volume that sets the value of a drop
The steps: Rinse, fill, add drop by drop, countShaking after each drop
Waiting time: NoneThe colour change is immediate, there is no colour development to wait for
Total time: About 2 minutesThe harder the water, the more drops you have to count
Recommended frequency: 1 per day, then 1 per weekEvery day for the first week after filling, then as a routine
Water types covered: Freshwater and garden pondThis test is not for use in seawater

Hazard labelling

Signal word: WarningThe single bottle in the kit
Pictograms: Flame and exclamation markGHS02 and GHS07
Hazard statements: H226, H315, H319Flammable liquid, skin irritation, serious eye irritation
Precautionary statements: P101, P102, P303+P361+P353, P305+P351+P338, P501Bottle or label to be shown to the doctor, keep children away, rinse skin and eyes, dispose of the empty bottle according to regulations
Precautions: Sink, ventilated room, out of reachChild-resistant cap, bottle kept away from any flame
Classified components: Triethanolamine, ethanolWith a little ammonia and EDTA

To allow for in addition

What you need to remineralise: A shrimp salt, or Epsom saltThe first raises the whole GH, the second only the magnesium share without affecting carbonates
Reagent refill: Reagent only, ref. 2410900The graduated test tube keeps well

12 further specifications are available in the detailed view.

In the box

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

Manufacturer's values (instructions for use and safety data sheet for the GH reagent). Aquaponic benchmark from the FAO.

Manufacturer and product safety

Manufacturer: JBL GmbH & Co. KG
Postal address: Dieselstraße 3, 67141 Neuhofen, Allemagne
Contact: info@jbl.de
Website: www.jbl.de

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

Total hardness, in which kit?

Same manufacturer, same drop reagents. The 6-in-1 kit covers the nitrogen cycle and pH; total hardness is found in this test on its own and in the 13-in-1.

A moulting shrimp needs calcium in the water Below 5 °dGH, moulting fails and shells become pitted. Above 25 °dGH, most freshwater fish and plants fall outside their ideal keeping range.

	Parameters covered	Drop test kits included	Total hardness GH	Carbonate hardness KH	pH, nitrite, nitrate and ammonium	Iron, phosphate, copper and oxygen	Reagent bottles	Glass test tubes	Laboratory comparator block	Thermometer	Reagent refill sold separately	Price
Recommended Total hardness test onlyYour choice	1	1	Yes	No	No	No	1	0	No	No	Yes	1,200.00 RSD
6-in-1 Aquarium Water Testing KitYour choice	6	5	No	Yes	Yes	No	9	3	Yes	No	Yes	6,200.00 RSD
JBL ProAquaTest Lab water analysis case, 13 tests for aquarium and pondYour choice	12	13	Yes	Yes	Yes	Yes	23	12	Yes	Yes	Yes	12,000.00 RSD

Total hardness test onlyRecommended

What you are measuring

Parameters covered1

Drop test kits included1

Total hardness GHYes

Carbonate hardness KHNo

pH, nitrite, nitrate and ammoniumNo

Iron, phosphate, copper and oxygenNo

Equipment supplied

Reagent bottles1

Glass test tubes0

Laboratory comparator blockNo

ThermometerNo

Budget

Reagent refill sold separatelyYes

6-in-1 Aquarium Water Testing Kit

What you are measuring

Parameters covered6

Drop test kits included5

Total hardness GHNo

Carbonate hardness KHYes

pH, nitrite, nitrate and ammoniumYes

Iron, phosphate, copper and oxygenNo

Equipment supplied

Reagent bottles9

Glass test tubes3

Laboratory comparator blockYes

ThermometerNo

Budget

Reagent refill sold separatelyYes

JBL ProAquaTest Lab water analysis case, 13 tests for aquarium and pond

What you are measuring

Parameters covered12

Drop test kits included13

Total hardness GHYes

Carbonate hardness KHYes

pH, nitrite, nitrate and ammoniumYes

Iron, phosphate, copper and oxygenYes

Equipment supplied

Reagent bottles23

Glass test tubes12

Laboratory comparator blockYes

ThermometerYes

Budget

Reagent refill sold separatelyYes

Kit contents taken from their data sheets. A titration needs neither a comparator block nor a glass test 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

Estimate your
delivery time

Parcel of 0.09 kg, dispatched within 48 h by Colissimo or Chronopost home delivery, as you choose during payment. The reagent is sent in its original box. The exact amount is shown in the basket. Once unsealed, this product can no longer 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 GH do shrimp need?

I've measured my GH and my pH hasn't changed, why?

My RO water shows zero, what should I add?

First decide on your target, as it depends on what you are keeping.
Blend the osmosis water with tap water, in the proportion this test gives you in 2 minutes.
Or add the minerals separately, using a remineralising salt for shrimp.
Always retest: a dose printed on a sachet does not take your starting water into account.

A hardness of zero means water with no calcium or magnesium, which must be remineralised before any animals or plants are introduced.

My snails have eroded shells, is it the GH?

How can I get more accuracy on very soft water?

In aquaponics, should you monitor GH?

Less than KH, but it matters when the system houses shrimp or snails, and when the top-up water is very soft. Rainwater used as top-up lowers GH month after month, and a summer top-up from the mains raises it, with nothing else to signal it.

The FAO guide puts the optimum hardness between 60 and 140 mg/L expressed as calcium carbonate, or roughly 3 to 8 °dGH. To check it, test a sample: the reagent never goes into the water with the fish.

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GH water test, total hardness, drop-based

The summary