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Streamline Your Aquarium Water Testing with LAQUAtwin

Testing aquarium water, such as freshwater and saltwater (natural or artificial seawater), with reliable instruments is necessary to create a clean and safe environment for your aquatic species.

Maintaining proper aquarium water chemistry is essential for the well-being of fish and other aquatic species. Aquarium enthusiasts utilise saltwater, whether it’s natural or artificial seawater, in fish-only, fish-only with live rock (FOWLR), and reef tanks. Conversely, freshwater is employed in planted, biotope, cichlid, brackish, and predator tanks. Generally, saltwater setups are more costly and demanding to maintain due to the requirement for additional equipment and frequent testing.

Regular maintenance activities such as filtration, water changes, and testing are necessary to ensure excellent water quality. For a precise analysis of your water chemistry, the LAQUAtwin pocket meters offer a convenient solution. These meters require only a few drops of water and provide results within seconds, making them a handy tool for your testing needs.

When it comes to evaluating the saltwater parameters of a reef aquarium, Reefkeeping Online Magazine offers valuable guidelines. In Tables 1 and 2 below, you’ll find a summary of key factors to take into account followed by an explanation of their significance in the analysis process for reef and other aquarium types.

Parameters to Analysis


Calcium is an essential element for coral health in a saltwater aquarium. Corals use it to form their skeletons, composed primarily of calcium carbonate. When the calcium level in water drops below 360ppm or becomes depleted, corals face challenges in acquiring the necessary calcium for their growth. To address this, one can add calcium chloride (CaCl2) to the water in order to increase the calcium level.


Alkalinity, also known as carbonate hardness, arises from the presence of carbonate (CO32-) and bicarbonate (HCO3-) anions. It can be measured in either parts per million (ppm or mg/L) or degrees KH (dKH).One dKH is equal to 17.848 ppm CaCO3. Like calcium, alkalinity is also essential for the skeletons of corals. Corals are believed to take up the bicarbonate, convert it to carbonate, and then use that to form calcium carbonate skeletons. As a result, experts recommend utilising balanced calcium and alkalinity additive systems such as limewater, calcium carbonate, and two-part additive systems for regular maintenance. Where quick alkalinity correction is necessary, baking soda or washing soda are recommended options.


Salinity measures the concentration of all salts dissolved in water. It is related to the concentration of dissolved salts in seawater. The main difference between fresh water and salt water is the salinity content. Fresh water contains only a small amount of salt. Too much or too little salt will adversely affect the health of fish. The recommendation is to target the natural seawater salinity value of 35 ppt. To create this natural environment, add more fresh water if the salinity is high or increase the amount of salt mixture if the salinity is low.

You can directly measure salinity using a salt meter or indirectly determine it through a conductivity meter. For example, seawater’s 35 ppt salinity value (specific gravity = 1.025) is equivalent to 53 mS/cm conductivity.


The best water temperature depends on the species in the aquarium. In general, tropical fishes are healthy at 24 – 28ºC. Cold-water fishes, like goldfish, enjoy water below that temperature range. Ensure a stable temperature, as rapid, drastic and frequent temperature changes throughout the day are stressful for fish.
Another critical factor to note is the oxygen availability to fish. Oxygen is less soluble in water at higher temperatures.


pH, which stands for the power of hydrogen, is the measurement of hydrogen ions in a solution. This gives us the acidity or alkalinity of water from a scale of 0 to 14. The carbonate hardness and calcium level in water affect the pH value. The optimal pH also depends on the species in the aquarium. For most species to survive, the pH of the water should be close to pH 8.2 of natural seawater.

There are several ways to adjust the pH in seawater.

  1. To raise pH: Add crushed corals, limestones, or baking soda, or perform aeration.
  2. To lower the pH: Add driftwood or peat.

Remember to adjust the pH slowly, as rapid, drastic and frequent pH changes could kill your species


Magnesium is another element corals use for growing their calcium carbonate skeletons and coralline algae for their calcium carbonate deposits. Natural seawater contains an abundance of magnesium, and it is important to measure it, especially if maintaining the aquarium’s calcium and alkalinity levels proves challenging. The magnesium concentration should be close to 1280ppm of natural seawater.


High phosphate levels inhibit the calcification or building-up of calcium carbonate skeletons of coral and coralline algae. Above 0.03 ppm, algae growth is uncontrollable. Thus, keeping the phosphate concentration below 0.03ppm will deter algae growth.
To maintain low levels of phosphate, apply phosphate export mechanisms, such as growing and harvesting macroalgae or other rapidly growing organisms. Another way is to use limewater, phosphate-binding media, or foods without excessive phosphate.


All aquatic animals excrete ammonia, which is considered toxic to them, even at low levels as low as 0.2 ppm. The ammonia level in water increases as the pH level rises. In this instance, transfer the fish to cleaner water or treat the aquarium with an ammonia-binding product.
The LAQUAtwin pocket meters measure and monitor freshwater or saltwater in aquariums. The meters have flat sensors for quick, direct and accurate measurement of micro-volume water samples without adding any chemicals.

Testing using the LAQUAtwin Meters

Using the LAQUAtwin pocket meters can simplify the process of measuring and monitoring water parameters in both freshwater and saltwater aquariums. These meters offer quick, direct, and accurate measurements of micro volume water samples without the need for adding any chemicals.

To use the meters effectively, calibrate them according to the manufacturer’s instructions using the provided standard solutions. When measuring a sample, you can either place a few drops of aquarium water onto the sensor using a pipette or immerse the sensor directly into the aquarium by opening the sensor guard. Rinse the sensor with deionised water and gently blot it dry with a soft tissue between samples.

When measuring a sample, you may allow the meter to lock the stable reading by pressing the MEAS button. This activates the auto-hold function—MEAS will blink until the reading is stable and will appear. Press MEAS button again to deactivate the auto-hold function. Note: For pH, salt, and conductivity meters, make sure to set auto-hold (AH) in the meter settings before measurement.

For additional details on sensor conditioning, cleaning, and storage, you can refer to the technical tips provided by the manufacturer.

Table 3 below shows an example of results of LAQUAtwin pocket meters in artificial seawater measurement. The results were compared against the values indicated on the product label.

LAQUAtwin Meters

To assist with water testing in your aquarium, the following LAQUAtwin meters are worth considering:

Salinity and Conductivity

The Salt-11 meter is programmed with sodium chloride (NaCl) and seawater curves. For this application, the seawater curve is suitable. The meter displays both salinity and temperature readings.
The EC-11, EC-22, or EC-33 conductivity meters can indirectly be used to determine salinity. After obtaining the conductivity value, refer to Table 4 to check the corresponding salinity value.


The pH-11, pH-22 or pH-33 LAQUAtwin meters have a temperature compensation function, but only the pH33 meter displays the temperature reading. For accurate measurement, calibrate the meter with at least two pH buffers that bracket the expected sample pH. If the expected pH is 8.0, select USA buffer setting and calibrate the meter using pH 7.00 and 10.01 buffers or select NIST buffer setting and calibrate using pH 6.98 and 9.18 buffers.

Calcium, Sodium, Potassium, and Nitrate Ions

The Na-11 (previous model B-722), K-11 (previous model B-731), and Ca-11 (previous model B-751) LAQUAtwin meter measure the free sodium ion, potassium ion, and calcium ion, respectively. All the results obtained in artificial seawater measurement have less than 10% error.

In nitrate ion measurement, chloride ion in seawater is one of the interfering ions. The chloride ion concentration in seawater is around 20,000 ppm and will affect the nitrate ion concentration. The target nitrate concentration in aquarium water is less than 0.2 ppm. The NO3-11 (previous model B-743) LAQUAtwin meter measures nitrate in the 6 to 9900 ppm range.

In conclusion, maintaining optimal water quality in your aquarium is crucial for the health and well-being of your aquatic species. By regularly testing and monitoring key parameters such as pH, temperature, salinity, calcium, alkalinity, magnesium, phosphate, and ammonia, you can create a clean and safe environment.

Should you require further information or assistance, refer to the references and suggested readings below or contact our technical department at Camlab.

  1. Saltwater Versus Freshwater Aquariums by Katherine Barrington http://www.ratemyfishtank.com/blog/saltwater-versus-freshwater-aquariums
  2. Reef Aquarium Water Parameters by Randy Holmes-Farley http://reefkeeping.com/issues/2004-05/rhf/
  3. AquariumDetective.com http://aquariumdetective.com/articles/watertest.php

The technical department at Horbia supplied content for this article.

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