GH Test (total hardness)
User manual
Understanding and adjusting the GH value
The GH is the so-called total hardness or in German Gesamthärte, abreviated to GH. The GH is the total amount of dissolved minerals like calcium and magnesium; in practice about 90% of the GH is made up out of calcium, the remaining 10% is magnesium. These minerals are important substances for fish health but also for a good growth of water plants.
In case of an adequate GH, these minerals do not limit the plant growth and thus plants can grow optimal. Optimal plant growth is the natural way for blocking algae growth, and thus an optimal GH is also important for clear water and keeping away (thread)algae. Thus, test the GH regularly and refresh 10% of the water weekly.
An optimal GH-value in fresh water (both aquaria as well as ponds) is between 10 and 15°DH. When the GH is above 15°DH, the water is too hard and white deposits in the form of lime can occur. You can lower the GH by refreshing water; first check the GH and add Colombo Fish Protect to the fresh water. When the GH is lower than 8°DH, you can increase it with Colombo GH+.
General Guidelines
- Always take care that the test tube is clean before use.
- Clean the tube directly after use.
- Take the volume of the water sample as precisely as possible.
- Keep the drop bottle perfectly vertical during dropping.
- Take care that no air bubbles are included in the drops.
Test procedure:
- Take a water sample of 5 ml.
- Add 1 drop of GH-test fluid and mix. The sample should turn red; when it turns green, the GH of the water is lower than 1°DH.
- Add GH-test fluid drop by drop and mix each time, until the sample turns green.
- The number of drops added to induce the colour change from red to green, is equal to GH-value in °DH, so 2 drops =2°DH, 3 drops =3°DH and so on.
Test procedure:
- Take a water sample of 5 ml.
- Add 1 drop of GH-test fluid and mix. The sample should turn red; when it turns green, the GH of the water is lower than 1°DH.
- Add GH-test fluid drop by drop and mix each time, until the sample turns green.
- The number of drops added to induce the colour change from red to green, is equal to GH-value in °DH, so 2 drops =2°DH, 3 drops =3°DH and so on.
In the test where drops are to be counted, like KH and GH, the moment at which the colour changes is the point at which the true value is reached. The number of drops added to reach that point can be converted to the true value. The colour change is reached within one or two drops. Within the one or two drops the sample has an intermediate colour. The true end value is only reached when the colour doesn’t change anymore. These Colombo-tests are calibrated with professional laboratory tests, ensuring the most precise test possible.
In the test where drops are to be counted, like KH and GH, the moment at which the colour changes is the point at which the true value is reached. The number of drops added to reach that point can be converted to the true value. The colour change is reached within one or two drops. Within the one or two drops the sample has an intermediate colour. The true end value is only reached when the colour doesn’t change anymore. These Colombo-tests are calibrated with professional laboratory tests, ensuring the most precise test possible.