Water Testing
One of the most important things to have on hand for an aquarium hobbyist is a master test kit that can test for ammonia, nitrite, nitrate, and pH. Additionally if you plan on keeping fish that are adapted to a different hardness and alkalinity than what your source water is, then you will also need a general hardness and alkalinity test kits. When selecting which brand of aquarium test kit to buy, I recommend you get the test kit you find easiest to use, because a test kit that is difficult to use is less likely to be used.
A pH reading can change depending on the time of day the water is tested. If you test the water early in the morning the pH reading can be several tenths of a point lower than a test taken in the evening before the lights are turned off. The reason for this is because during the night the plants take up oxygen and give off carbon dioxide. Carbon dioxide combines with carbonate to form carbonic acid. Carbonic acid drives the pH down. When the lights come on, plants take up carbon dioxide and produce oxygen, driving the pH up. You should test the pH at least once every two weeks on an established aquarium. A lower than expected pH reading can often indicate excessive nitrate accumulation in the water, and/or low alkalinity.
After an aquarium has been setup for a week with fish it should be tested for ammonia every two or three days. Aquarium ammonia test kit results give a reading that is actually a combination of two chemicals NH3 (un-ionized ammonia) and NH4+ (ionized ammonia known as ammonium) known as total ammonia nitrogen. If any ammonia is detected in the test results you must then test the pH of the aquarium. You then can enter the result of the two tests along with the water temperature in celsius in the Free Ammonia Part of TAN tool provided previously in this book to extract the toxic free ammonia NH3. If toxic or near toxic ammonia levels are detected, a water change will be required to reduce the concentration. Once the ammonia concentration in a new aquarium starts to drop without doing any water changes, you can then test every five days until it drops to 0 ppm. In an established aquarium you should not have to test for ammonia unless your fish look stressed, or you have unexplained deaths.
In an established aquarium you should not have to test for ammonia unless your fish look stressed, or you have unexplained deaths. Some things that have been known to cause elevated TAN readings in an established aquarium are:
- Power outage for an extended period
- Gravel cleaning with a gravel vacuum on a tank that does not have an undergravel filter
- Cleaning a sponge filter
- Cleaning a canister filter
- Low aquarium pH
- Antibiotics
The toxicity of NH3 is highly variable depending on the species of fish. Damage to fish organs can occur with exposure to low levels of NH3 for an extended period of time. The below table provides some conservative general guidelines to follow for determining how toxic the NH3level is in the aquarium:
| NH3 ppm | Affect on Fish |
|---|---|
| 0.020 - 0.049 | Can cause long term harm that will affect growth, immune system, and health, especially to eggs and fry |
| 0.050 - 0.199 | Can be tolerated for only a few days and is harmful |
| 0.200 - 0.499 | Can be tolerated for a 24 to 48 hours and may kill some species of fish |
| >0.500 | Deadly to some species of fish within 24 hours of exposure |
Nitrite levels in a new aquarium will normally start to rise about two weeks after it has been set up with fish. At two weeks you should start testing nitrite levels at least once every two days. Nitrite levels will usually peak at about three and a half weeks after adding fish to a new aquarium. Nitrite levels should be down to near 0 ppm at around 35 days. If toxic (=> 2 ppm) or near toxic nitrite levels are detected, a water change will be required to reduce the concentration. Once the nitrite concentration in a new aquarium starts to drop without doing any water changes, you can then test every five days until it drops to 0 ppm. Once the ammonia and nitrite levels stay at 0 ppm the aquarium is then considered cycled.
Nitrate in most freshwater aquariums will accumulate over time. How fast it accumulates will depend on stocking densities, feeding, live plants, and light intensity and duration.
In a low stocked aquarium with live plants and high intensity lighting, it is possible to have no noticeable nitrate build up. An aquarium that does not have any nitrate build up is considered balanced and should be what all aquarist strive to achieve.
You should start testing nitrate level after a new aquarium has been set up for two months. If you have any nitrate build up, this should give you an initial idea of how fast nitrate will build up with the current bio-load. You should continue to test the nitrate several times a year to make sure you are keeping nitrate under control.
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.
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.
Carbonate Hardness or KH, measures the alkalinity. KH refers to the concentration of bicarbonate (HCO3-) and carbonate (CO3--) dissolved in water. Carbonate Hardness measures the buffering capacity of the water. The higher the concentration the more resistant the water is to pH fluctuation. This test kit is usually targeted for marine (saltwater) 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 carbonate hardness test kits measure in degrees of hardness, based on a German scale and is represented by “dKH” or “KH” acronym. If the test kit you use tests on a dKH scale, you will need to multiply the results times 17.86 to convert to ppm.
A system with a higher KH level can help reduce the pH lowering effect nitrate has on the aquarium ecosystem.
Total Dissolved Solids meter will check the water for all elements dissolved in the water (ie. salt, calcium, carbonate, bicarbonate, magnesium). This meter a valuable tool in figuring out exactly how much in parts per million of dissolved solids have been added when adjusting the water chemistry. You can usually find these meters for less than $30.
TDS meters are also used to measure the effluent of reverse osmosis filtration systems to determine if a membrane needs to be replaced. If the TDS is elevated beyond an acceptable value, it is then time to replace the membrane.
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 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.