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JBL GH Test Set

by JBL
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SKU J25350
  • Simple and reliable control of water values in ponds/aquariums. Determines the ideal total hardness for freshwater aquariums and ponds.
  • Colour change test: fill plastic cuvette with sample water, add reagent drop by drop until colour changes from red to green.
  • Number of drops = level of GH (total hardness).
  • When to use: for setting up a new aquarium: once a week.
  • Online Laboratory: regular control for a healthy aquarium/pond with conditions close to nature.
  • JBL has water tests in the form of quick tests or colour change tests for every water analysis.
  • Testing aquarium water for healthy, clear water.
  • Package contents: 1 quick test, GH Test. Incl. reagent and plastic vial. Refill reagent avaiable separately.


Healthy aquarium/healthy pond with conditions close to nature:

  • The right water values are dependent on the fish stock and the plants in the aquarium/pond.
  • Even if the water looks clear it can be contaminated.
  • With bad values diseases or algae can appear in the aquarium/pond.
  • To maintain a healthy aquarium/pond with conditions close to nature it is important to check and adapt the water values regularly.
  • For each water analysis JBL provides water tests in the form of quick tests or colour change tests.
  • These determine a certain value or several values in one go.
  • With these water tests you can recognise algae problems and negative nitrate, nitrite, potassium, magnesium values etc.

Why test?

  • Depending on origin and consistency of the subsoil, water may contain varying quantities of alkaline earth salts, usually in the form of calcium and magnesium salts.
  • General hardness, by definition, is the sum of calcium and magnesium ions suspended in the water.
  • Most fish and plants thrive well at a general hardness of between roughly 8 and 20°dH.
  • Excessive total hardness values, should, however, be counteracted by the appropriate measures.

JBL Online Laboratory:

  • Regular control for a healthy aquarium/pond with conditions close to nature.
  • Enter your water values into the JBL Online Laboratory and get an in-depth analysis of your values within seconds.

Recommended general hardness values:

  • Freshwater aquarium (community aquarium): 8-25 °dGH
  • Lake Malawi/Lake Tanganyika aquarium: 5-20 °dGH
  • Plant aquarium with few fish (aquascaping): 3-10 °dGH
  • Marine aquarium: not measurable with GH test because GH too high. Please test calcium and magnesium separately
  • Pond: 6-20 °dGH


Where can I find the record sheets for the documentation of my water analysis?

> Have you lost your record sheets, already filled them all in or do you need them in another language?

With the following links you can quickly and easily print out your new record sheets with recommendations for the individual parameters at home and document the water analyses.

Why are there no colour charts for GH. KH, Mg /Ca saltwater and CO2 direct?

> The tests from the test range: JBL GH test, JBL KH test, JBL calcium test Ca and JBL magnesium test Mg, where the number of drops are counted until the colour changes and the counted value is multiplied by a value:

GH = number of drops = general hardness in °dH

KH = number of drops = carbonate hardness in °dH

CO2 = number of drops * 2 = CO2 in mg/l

Magnesium + calcium = number of drops * 120 = amount Ca + Mg in mg/l

Calcium = number of drops * 20 = amount Ca in mg/l

Magnesium = amount Ca+Mg from magnesium test - amount Ca in mg/l = magnesium in mg/l

What can I do when the measured value of a water test falls outside the scale?

> If one of your measurements reaches the end of the colour chart scale you can multiply the scale by diluting later tests with distilled water (e.g. JBL Dest).

Here’s how to do it: dilute the sample with distilled water and carry out the test once more.

This works in detail as follows:
GH test: Instead of 5 ml use 10 ml aquarium water. Now 1 drop is equivalent to 0.5 dGH.

KH test: Instead of 5 ml use 10 ml aquarium water. Now 1 drop is equivalent to 0.5 dGH.

Note: when using 10 ml sample water the colour development is weaker with the first drops than with 5 ml sample water. Put the measuring container on a white underlay for a better readability.

NH4/NH3 ammonium/ammonia, NO2 nitrite, Fe iron and Cu copper:

2.5 ml sample + 2.5 ml dist. water: result times 2

1 ml sample + 4 ml dist. water: result times 5

0.5 ml sample + 4.5 ml dist. water: result times 10

NO3 nitrate, SiO2 silicate, PO4 phosphate sensitive and Mg magnesium freshwater:

5 ml sample + 5 ml dist. water: result x 2

2 ml sample + 8 ml dist. water: result x 5

1 ml sample + 9 ml dist. water: result x 10

PO4 phosphate koi high range:

2.5 ml sample + 2.5 ml dist. water: result x 2

1 ml sample + 4 ml dist. water: result x 5

K potassium:

7.5 ml sample + 7.5 ml dist. water: result x 2

3 ml sample + 12 ml dist. water: result x 5

1.5 ml sample + 13.5 ml dist. water: result x 10

K potassium in marine water:

1. Fill 10 ml of sample water with distilled water to 300 ml.

2. Follow the instructions for fresh water.

3. Multiply the test result by a factor of 30.

CO2 direct, Ca calcium and Mg+Ca magnesium+calcium: not required.

What is the shelf life of the JBL GH-Test ?

The JBL GH test has a shelf life of 2 years in the original sealed bottle.

The following is printed on the bottom of the packaging:

CH/B: 2253 (e.g.) = batch number

BBD: 05/13 (e.g.) = best-before date.

Please note that the best-before date does not apply for opened reagents. Exposure to atmospheric oxygen decreases the shelf life.

Do my water tests still work although they have been open for nine months?

> Basically a sealed test keeps longer than an open one. How much the shelf life is reduced depends crucially on the handling and the storage conditions of the reagents. It may happen that a reagent in a test that has been open for 9 months doesn’t indicate correctly any more. However, additional information is needed to answer this question properly.