Mastering Freshwater Aquarium Ecosystems
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Water Testing (Cont.)

If the pH test indicates the aquarium system has a very low pH (below 6.0), but the nitrate reads zero or near 0 ppm, this could indicate that you are incorrectly using your nitrate test kit, or your nitrate test kit is giving a false low reading.

Nitrate Test

If you have difficulty reading test results cutting the aquarium water with nitrate free water can help make the concentration of nitrate easier to read. Above is the nitrate test results from the same aquarium. Vial on the far right is 100% aquarium water, the middle vial is 50% aquarium water and 50% nitrate free water, and the left vial is 25% aquarium water and 75% nitrate free water. In this case the middle vial results would be multiplied by two and the far left vial would be multiplied by four to get the results. All three tests confirm that the nitrate in this case is 40 ppm.

If nitrate test indicates that your aquarium nitrate concentration is at the top of the chart or off the chart (not that uncommon), you may need to cut the aquarium water with a known source of nitrate free water (bottled water, distilled, most tap water).  In some cases you may have to use one part tank water to 19 parts nitrate free water.  Mix the water together then test.  Multiply the results by 20 to get an accurate result.  You will need to adjust how much you dilute the aquarium water before testing based upon how much nitrate you suspect may be in the water.

Nitrate should not be allowed to exceed 100 ppm for more than two weeks. If nitrate accumulates quickly in your aquarium system, it may require frequent large volume (>75%) water changes to keep it under control.

General Hardness (GH)

General hardness test kit measures of calcium and magnesium ions dissolved in water. This test kit is usually targeted for soft water aquarium hobbyist, but should also be considered by freshwater hobbyist that want to keep Lake Malawi, Lake Tanganyika, and Central and South American livebearers. Many general hardness test kits measure in degrees of hardness, based on a German scale and is represented by “dH” or “dGH” acronym.  If the test kit you use tests on a dH scale, you will need to multiply the results times 17.86 to convert to ppm.

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