Monitoring the water quality in your aquarium with the Pocket Testers from HORIBA
Correctly assess water quality in the aquarium
Experienced aquarists know how important water quality is in the aquarium and determine the relevant parameters using various tests. Regular examination and analysis of the present situation, regardless of the external appearance of the aquarium, improves the well-being and ultimately also the breeding behaviour of the aquarium inhabitants.
Testing aquarium water, such as fresh and salt water (either natural or artificial seawater) with reliable instruments is necessary to provide a clean and safe environment for your aquatic species. The LAQUAtwin pocket meters, are easy to handle, require only a few drops of water and provide the measurement results in a few seconds.
Which values are particularly important for an aquarium?
The most important water values are summarised below:
- The total hardness (GH)
- Carbonate hardness (KH) or acid binding capacity
- The pH value
- The carbon dioxide value (CO2)
- The chloride content (Cl2)
The most important values, the concentration of which should always be checked about once a week, are nitrite, nitrate, the pH value and the water hardness (total hardness and carbonate hardness). In addition, the values for ammonium, chlorine and copper can be relevant for keeping animals in aquarium water. For a good plant population in the aquarium, water values such as carbon dioxide, iron, magnesium and phosphate should be monitored.
The pH value
In the field of aquaristics, the pH value should be between 5.0 and 8.5. Values above or below this scale represent rather extremes that are rarely or never used in aquaristics. A pH value of 7 is considered neutral, whereas values below this are acidic and values above 7 are alkaline. Acidic, or soft water, is often used in the maintenance of blackwater aquariums, but also for South American perches and tetras, as well as for shrimps of the genus Caridina. Alkaline pH values, on the other hand, are more common in hard-water aquariums such as some perches, but also in brackish water and marine fish.
Constant maintenance of a suitable pH value is an important prerequisite for the well-being of the aquarium inhabitants and all aquatic organisms. Sudden and strong fluctuations (when the pH value drops, there is also talk of so-called "pH crashes") should be avoided at all costs. In addition, many substances dissolved in the water are subject to changes depending on the pH value.
For example, the amount of CO2 that can be dissolved in the water is directly related to the pH value.
For this reason, the pH value can serve as a control variable for the adjustment of CO2 fertilisation systems, provided that there are no other acids (e.g. humic acids) in the water that influence the pH value apart from CO2. With pH values between 6.8 and 7.3, a CO2 concentration that is considered harmless for most plants and fish is achieved.
A pH value of 8.2 is considered optimal, especially for marine animals. In particular, lower animals, so-called invertebrates, such as corals, can cause the pH value and also the carbonate hardness to drop through their consumption of calcium bicarbonate if regular replenishment is not provided. In the garden pond, on the other hand, a pH value between 7.5 and 8.5 should be aimed for.
In the case of a CO2 deficiency, algae can quickly consume the hydrogen carbonate available in the water due to their rapid adaptability in the course of their photosynthesis and thus drive the pH value up.
With the HORIBA pH Pocket Tester of the LAQUAtwin series you can easily determine the pH value in your aquarium.
Horiba LAQUAtwin pH Tester
HORIBA pH Handheld Tester – Ideal for Water and Environmental Analysis Precise pH measurements on-site – compact, reliable, and easy to use The Horiba LAQUAtwin pH tester is ideal for water quality testing in rivers, drinking water, and process water. With a measurement range of 0.0 to 14.0 pH and a 2-point calibration, the tester is suitable for a wide range of pH analyses. Just a single drop of sample provides quick and reliable measurement results. The tester combines electrode, display, and sample container in a robust IP67-rated housing that is dust- and waterproof. The digital display with backlight shows both pH and mV values. Features such as automatic stability detection and Auto-Hold simplify operation. With up to 400 hours of battery life, the tester is suitable for extended measurement series. Included are calibration buffer solutions (pH 4.01 & 7.00), batteries, pipette, instruction manual, and a carrying case. Handheld pH tester for fast and precise results With its wide measurement range and 2-point calibration, the Horiba LAQUAtwin pH tester is suitable for a variety of pH analyses. Even a single drop of sample is enough to obtain fast and accurate results. Its compact design makes the mobile pH tester highly user-friendly and allows on-site measurements without complex sample preparation or laboratory infrastructure. Robust, waterproof design with comprehensive features The tester integrates the electrode, display, and sample container in a robust IP67-rated housing that is dust- and waterproof. The digital backlit display clearly shows pH and mV values. Features like automatic stability detection and Auto-Hold simplify daily use. With a battery life of up to 400 hours, the tester is suitable for long measurement series. The package includes calibration buffer solutions (pH 4.01 & 7.00), batteries, pipette, instruction manual, and a practical carrying case. Typical applications of the Horiba LAQUAtwin pH Pocket Tester Aquaculture and corals Aquariums Beer, beverages, and food Heating systems Laboratories and schools Horticulture Water treatment
Mobile pH Tester with 3-Point Calibration for On-the-Go Use Horiba LAQUAtwin pH Tester – ideal for water and environmental analysis The Horiba LAQUAtwin pH Tester pH-22 is compact, robust, and designed for mobile use. With up to three calibration points and a measurement range of 0.00 to 14.00 pH, this device delivers high precision and reliability. Direct measurement with just a single drop of sample provides fast results. Features such as automatic buffer recognition, temperature compensation, and Stabil/Hold functionality make daily operation simple and convenient. Mobile precision pH tester for reliable on-site measurements The tester combines electrode, display, and sample container in a dust- and waterproof IP67 housing, making it ideal for field and laboratory applications. The digital backlit display shows pH and mV values clearly and accurately. Automatic shut-off and battery status indicators ensure convenient operation. The package includes calibration buffer solutions (pH 4.01 and 7.00), batteries, a pipette, and a quick-start guide. Why accurate pH measurement is critical – and why a handheld tester is ideal pH is a key parameter in water, environmental, and process analysis because it significantly influences chemical reactions, biological processes, and material stability. Even small deviations can substantially impact water quality, product quality, or process safety. A mobile handheld pH tester allows fast, reliable measurements directly on site. Changes can be detected immediately, and corrective actions implemented without delay. The Horiba LAQUAtwin pH-22 combines this flexibility with high measurement precision, making it ideal for field, laboratory, and routine applications. Typical applications for the Horiba LAQUAtwin pH handheld tester Aquaculture and coral monitoring Beer, beverage, and food production Heating systems Laboratories and schools Environmental analysis Water treatment Horticulture
Manufacturer Part No. 3999960124 LAQUAtwin PH-33: The world's first pocket-sized PH meter Your mobile laboratory - for use on site: Ideal for water quality testing in aquatic, drinking and process water and many other applications. HORIBA's unique compact meter integrates electrode, display and sample container to enable simple, effective on-site testing by direct measurement with a single drop. Minimum sample volume: 0.1 ml (0.05 ml with sampling sheet B) Up to 5 calibration points pH, mV and temperature display Automatic calibration Automatic buffer recognition: USA & NIST pH buffers Automatic temperature compensation Temperature calibration: 5 to 40.0 ºC Automatic stable / automatic hold measurement Automatic switch off: 30 min. Low battery indicator IP67 rating dust and waterproof Replaceable sensor 400 hours battery life: continuous operation without backlight Material: ABS epoxy Display: customised (monochrome) LCD with backlight Operating conditions: 5 to 40°C, 85% or less relative humidity Warranty: 2 years - meter, 6 months - sensor Packed in a practical carrying case Supplied with pH 4.01 & 7.00 buffers (14ml each), 2 x CR2032 batteries, dropper, instructions and quick reference guide
Manufacturer Part Nr. 3200459834
Total hardness (GH) and carbonate hardness - Measurement of calcium
Total hardness and carbonate hardness are the most important parameters for determining water hardness in aquariums. How does the total hardness differ from the carbonate hardness and what influence does it have on fish and plants?
Total hardness is the sum of the positively charged alkaline earth ions dissolved in the water. Calcium, magnesium, barium and strontium are counted as alkaline earths. However, the total hardness is mainly influenced by the content of positively charged calcium and magnesium ions (Ca2+ and Mg2+). For this reason, calcium and magnesium are also called hardness minerals.
Carbonate hardness, on the other hand, is based on the content of negatively charged hydrogen carbonate ions (HCO3-) dissolved in the water.
Since the total hardness, unlike the carbonate hardness, is not influenced by heating or boiling the water, it is also called permanent hardness, while the carbonate hardness is known as temporary hardness.
The unit of total hardness is given in degrees of German hardness (°dH). In addition to its significance for the aquarium biotope, the total hardness is also a decisive quality parameter for drinking water.
What does the total hardness actually mean for the aquarium?
In contrast to the carbonate hardness, the total hardness has no direct influence on the stability or the level of the pH value in the aquarium and also has no direct influence on other water values. Therefore, the total hardness is of less importance to aquarists than the carbonate hardness. However, fish in aquariums need calcium, a so-called hardness former, for example to build bones or bones and to form cell walls. Aquatic plants also need small amounts of calcium. Magnesium is important, among other things, for the function of muscles and nerves in fish. In plant metabolism, magnesium is indispensable for photosynthesis. It should be noted, however, that fish take up a large part of the calcium and magnesium they need through their food.
Calcium, for example, is also an essential element for the health of corals in a marine aquarium. It is used by the corals to form their skeleton, which consists mainly of calcium carbonate. When the calcium level in the water drops below 360 ppm or is depleted, it becomes difficult for the corals to collect calcium for their growth. In this case, calcium chloride (CaCl2) can be added to the water to increase the calcium content.
With the help of the Calcium Ion Hand Tester from HORIBA from the LAQUAtwin series, you can monitor the calcium content, i.e. the hardness former calcium, in your aquarium.
Horiba LAQUAtwin Calcium Ion (Ca2+) Tester
Mobile Calcium Ion Tester from Horiba with Temperature Measurement – precise, compact, robust Handheld Ca²⁺ pocket tester with 2-point calibration and temperature display – ideal for water and environmental applications The mobile Horiba LAQUAtwin calcium ion tester measures both the Ca²⁺ concentration and the temperature of a sample. Equipped with an ion-selective sensor, a digital LCD display, and a minimal sample volume of only 0.3 ml (0.05 ml when using the sampling sheet), it delivers fast and reliable measurement results. Thanks to the integrated temperature display and automatic temperature compensation, calcium values can be measured accurately even under changing environmental conditions – making the device ideal for mobile applications. Mobile calcium ion tester for precise on-site measurements With two calibration points and automatic standard recognition (150 and 2000 ppm), the device can be flexibly adapted to different measurement situations. Temperature-compensated measurement, multiplicative compensation, automatic stability and hold modes, as well as automatic shut-off ensure easy and reliable operation. The tester is dustproof and waterproof according to IP67 and offers a long battery life of approximately 400 hours. It is supplied complete with standard solutions, sampling sheets, pipette, and batteries. Why calcium measurement is important – optimal results with the Horiba handheld tester Calcium is a key parameter in water, environmental, aquaculture, and food analysis. Calcium concentration influences water hardness, biological processes, coral growth, and product quality in beverages and food. Deviations can lead to ecological, technical, or quality-related impacts. A mobile calcium handheld tester allows fast analysis directly at the point of use without complex laboratory procedures. This makes it possible to detect changes immediately and take timely action. The Horiba LAQUAtwin calcium tester combines this flexibility with high measurement accuracy, simple operation, and a robust design. Typical applications of the Horiba LAQUAtwin calcium tester Aquaculture and corals Laboratories and schools Water treatment Beverages and food
As a rule, soft to medium-hard water in the range of approx. 4 to 14 °dH is well suited for most freshwater fish and aquarium plants.
The total hardness in the aquarium increases, for example, due to the calcium and magnesium contained in the food, if the hardness builders are not sufficiently incorporated into the bones and bones of fish or into the shells of snails. If, for example, the snail population is very high, the total hardness may even decrease over time.
Recommended total hardness values:
- Freshwater aquarium (community tank): 8-25° dGH
- Malawi Lake Tanganyika aquarium: 5-20° dGH
- Planted aquariums with few fish (aquascaping): 3-10° dGH
- Saltwater aquariums: not measurable, as too high. Test calcium and magnesium separately.
- Ponds: 6-20 °dGH
Recommended carbonate hardness values:
- Freshwater aquariums (community tanks): 5-12° dKH
- Malawi-Tanganyika aquarium: 7-20° dKH
- Plant aquariums with few fish (aquascaping): 3-8° dKH
- Saltwater aquariums: 7-10 °dKH
- Ponds: 7-10° dKH
Nitrate (NO3), Nitrite (NO2), Ammonium (NH4) & Ammonia (NH3)
Monitoring the nitrate level is crucial because organic substances such as food and plant residues as well as fish excretions are degraded via the so-called nitrogen cycle. In the process, proteins are converted to ammonium, which in turn is converted to nitrite and finally to harmless nitrate. Various important bacteria are primarily responsible for this. With an appropriate nitrate test, conclusions can therefore be drawn about the health of the aquarium. Medication cures in particular can kill these important bacteria and thus lead to increased ammonium or nitrite levels. In a healthy aquarium, for example, ammonium, which is toxic to fish, is hardly detectable and serves as plant food. Especially in combination with CO2, however, deadly ammonia can be formed, which is why ammonium should always be measured together with CO2. Nitrite is also a strong fish poison that can be very harmful to young animals, invertebrates and especially marine fish. Even the smallest concentrations of 0.5 - 1.0 mg/l can be fatal.
If ammonium and nitrite are elevated, it can be assumed that the aquarium is out of its biological balance and the bacterial balance is irritated. If, on the other hand, the nitrate values remain high and the ammonium or nitrite content low or undetectable, the bacterial balance is intact. However, this is an indication that the balance between fish as nitrogen producers and plants as consumers is not right. Algae in particular start to "explode" if the nitrate content is too high and at the same time there is also a lot of phosphate. Therefore, nitrate levels below 30 mg/l in freshwater aquariums and below 20 mg/l in marine aquariums are considered ideal.
Check the nitrate content in your aquarium with the nitrate hand tester from HORIBA:
Horiba LAQUAtwin Nitrate Ion (NO3-) Tester
Horiba LAQUAtwin Nitrate Ion Tester NO3-11 for Precise On-Site Measurements Handheld tester with 2-point calibration, ideal for water and environmental measurements The Horiba LAQUAtwin Nitrate Ion Tester (NO3-11) is a portable device for direct determination of nitrate ions (NO3) and temperature in liquids and samples. Thanks to the ion-selective electrode and compact design, the tester delivers fast and reliable results. The integrated temperature unit enables temperature-compensated analysis and clearly displays both nitrate and temperature values on the digital LCD display. Mobile Nitrate Ion Tester for Precise On-Site Analyses The integrated temperature measurement enables temperature-compensated analysis and shows both nitrate and temperature values. Only very small sample volumes are required, minimizing sample consumption and increasing efficiency in daily use. The tester can be set up with up to two calibration points, with features such as automatic standard recognition, adjustable calibration values, and multiplication compensation for flexibility. Only minimal sample volumes are needed for each analysis, reducing sample usage and improving efficiency. Why Nitrate Measurement Is Crucial – and a Pocket Tester from Horiba Is Ideal Nitrate measurement plays a central role in agriculture, water management, and environmental monitoring. Elevated nitrate concentrations can affect drinking water quality, stress ecosystems, and contribute to over-fertilization. At the same time, nitrate is an essential nutrient for plants, and targeted control is vital for sustainable agriculture. A mobile nitrate pocket tester enables rapid on-site analysis without time-consuming laboratory tests. This allows early detection of contamination, immediate action, and reliable monitoring of legal limits. The Horiba LAQUAtwin NO3-11 combines this flexibility with high measurement accuracy and easy operation – ideal for routine checks and scientific applications. The tester can be configured with up to two calibration points. Features like automatic standard recognition, adjustable calibration values, and multiplication compensation provide high adaptability to different sample types and measurement conditions. Typical Applications of the Horiba LAQUAtwin Nitrate Ion Tester (NO3-11) Agriculture: To optimize fertilizer use, promote plant growth, and minimize environmental impact, farmers and agronomists use the tester to monitor nitrate levels in soils and irrigation water. Water Quality Management: To maintain nitrate concentrations within safe limits, the NO3-11 is used in water management to check drinking and wastewater quality. Environmental Monitoring: The NO3-11 allows environmental technicians and scientists to quickly analyze nitrate contamination in rivers, lakes, and groundwater, ensuring compliance with environmental standards and identifying pollution sources. Research and Development: The tester is used by scientists in environmental science, hydrology, and soil science to conduct detailed studies of the nitrogen cycle and the effects of nitrates on ecosystems.
Recommended nitrate values:
- Freshwater aquarium (community aquarium): 0-50 mg/l
- Malawi Lake Tanganyika aquarium: 0-50 mg/l
- Plant aquariums with few fish (aquascaping): 10-30 mg/l
- Saltwater aquariums: 0-20 mg/l
- Ponds: 0-10 mg/l
Conductivity (EC)
In addition, the conductivity value in the aquarium is an important indicator of the water quality. In aquaristics, the conductivity is used to control fully desalinated water, brackish water and seawater, as well as to control the salinisation of the aquarium water. Plants consume salts, thus lowering the conductivity, whereas feeding the aquarium inhabitants increases it. To a limited extent, conductivity can also be used as a control value for necessary maintenance measures such as water changes. Everything we put into the aquarium will cause our conductivity to rise. In the aquarium, conductivity values of less than 200 µS/cm are usually not a problem for many soft water fish, but the conductivity value in the aquarium should roughly correspond to the conductivity value of the fish's natural habitat. The conductivity of the water can be determined quickly and easily with a conductivity hand tester from HORIBA from the LAQUAtwin series.
Horiba LAQUAtwin Conductivity Meter
Manufacturer Part No. 3999960125 LAQUAtwin EC-11: The world's first pocket-sized conductivity meter Your mobile laboratory - for use on site: Ideal for water quality tests in aquariums, food, beekeeping (honey) and many other applications HORIBA's unique compact meter integrates electrode, display and sample container to enable simple, effective on-site testing by direct measurement with a single drop. Minimum sample volume: 0.12 ml Up to 2 calibration points Automatic range Automatic calibration Automatic standard detection: 1413µS/cm & 12.88mS/cm Automatic temperature compensation: 2%/ºC fixed Automatic stable / automatic hold measurement Automatic switch off: 30 min. Low battery indicator IP67 rating dust and waterproof Replaceable sensor 400 hours battery life: continuous operation without backlight Materials: ABS epoxy housing and titanium coating with platinum black sensor Display: customised (monochrome) LCD with backlight Operating conditions: 5 to 40°C, 85% or less relative humidity Warranty: 2 years - meter, 6 months - sensor Packed in a practical carrying case Supplied with 1413 µS/cm & 12.88 mS/cm conductivity standards (14ml each), conditioning solution (4ml), 2 x CR2032 batteries, drops, instructions and quick reference guide
Manufacturer Part No. 3999960126 LAQUAtwin EC-22: The world's first pocket-sized conductivity meter Your mobile laboratory - for use on site: Ideal for water quality tests in aquariums, food and many other applications. HORIBA's unique compact meter integrates electrode, display and sample container to enable simple, effective on-site testing by direct measurement with a single drop. Minimum sample volume: 0.12 ml Up to 3 calibration points Conductivity and temperature display Automatic range Automatic calibration Automatic standard detection: 1413µS/cm, 12.88mS/cm, 111.8mS/cm Automatic temperature compensation: 2%/ºC fixed Temperature calibration: 5 to 40.0 ºC Automatically stable / automatically held measurement Automatic switch-off: 30 min. Low battery indicator IP67 rating dust and waterproof Replaceable sensor 400 hours battery life: continuous operation without backlight Materials: ABS epoxy housing and titanium coating with platinum black sensor Display: customised (monochrome) LCD with backlight Operating conditions: 5 to 40°C, 85% or less relative humidity Warranty: 2 years - meter, 6 months - sensor Packed in a practical carrying case Supplied with 1413µS/cm & 12.88mS/cm conductivity standards (14ml each), conditioning solution (4ml), 2 x CR2032 batteries, dropper, instructions and quick reference guide
Manufacturer Part No. 3999960127 LAQUAtwin EC-33: The world's first pocket-sized conductivity meter Your mobile laboratory - for use on site: Ideal for water quality tests in aquariums, food and many other applications. HORIBA's unique compact meter integrates electrode, display and sample container to enable simple, effective on-site testing by direct measurement with a single drop. Minimum sample volume: 0.12 ml Up to 3 calibration points Conductivity, TDS and temperature display Automatic range Automatic calibration Automatic standard detection: 1413µS/cm, 12.88mS/cm, 111.8mS/cm Automatic temperature compensation: 2%/ºC fixed Temperature calibration: 5 to 40.0 ºC 4 curves for the total dissolved solids content: TDS factor 0.4 to 1.0, EN 27888, 442, NaCl Automatically stable / automatically held measurement Automatic switch-off: 30 min. Low battery indicator IP67 rating dust and waterproof Replaceable sensor 400 hours battery life: continuous operation without backlight Materials: ABS epoxy housing and titanium coating with platinum black sensor Display: customised (monochrome) LCD with backlight Operating conditions: 5 to 40°C, 85% or less relative humidity Warranty: 2 years - meter, 6 months - sensor Packed in a practical carrying case Supplied with 1413µS/cm & 12.88mS/cm conductivity standards (14ml each), conditioning solution (4ml), 2 x CR2032 batteries, drops, instructions and quick reference guide Horiba LAQUAtwin – Mobile Precision for Water Treatment The compact Horiba LAQUAtwin pocket testers deliver fast, accurate and user‑friendly on‑site measurement of key water parameters—directly from a single droplet. In the HeylNeomeris online shop, you’ll find carefully selected models designed for professional use in water treatment, environmental analysis, aquaculture, and laboratory routines. Why LAQUAtwin Devices Excel in Water Treatment: Ultra‑low sample volume: only 0.05 mL per measurement Rapid results: ideal for mobile checks and spot analyses Laboratory‑grade accuracy in a pocket‑sized instrument Effortless operation: no special training required IP67‑rated housing: waterproof, dustproof, and rugged for field use Key Applications in Water Treatment: Quick screening in drinking water testing or process water quality control Routine monitoring of parameters such as pH, conductivity, calcium, sodium, or nitrate Interim checks in laboratories or treatment plants where bench‑top instruments aren’t practical Perfect for service technicians, field engineers, and operators of small‑scale systems Sample Models Available in the HeylNeomeris Shop: Horiba LAQUAtwin pH‑11 – precision pH measurement Horiba LAQUAtwin EC‑33 – conductivity monitoring Horiba LAQUAtwin Na‑11, Ca‑11, NO₃‑11 – targeted ion analysis for sodium, calcium, and nitrate
Manufacturer Part Nr. 3200459672
Phosphate - PO4
In general, phosphate is an important plant nutrient and is mostly produced in the aquarium through the excretions of the fish, but also food remains. Too high phosphate levels, however, lead to undesirable algae growth, which occurs especially in heavily stocked waters. Natural and clean waters usually have a concentration of 0.01 mg/l and 0.07 mg/l in seawater. Algae in particular, but also higher aquatic plants, have assimilated to the general scarcity and therefore do not need large occurrences.
Phosphate levels really "explode" in the aquarium if the fish stocking is very high or too many excreta and food remains decay in the aquarium. But phosphate is also often added to drinking water for disinfection and decalcification. Algae in particular then multiply rapidly and are even able to store phosphate and can continue to grow even after a phosphate reduction cure.
Well-planted aquariums, on the other hand, can show the opposite: if plants grow weakly, there may be an underlying phosphate deficiency that should be compensated for with fertiliser.
You can check the phosphate levels in your aquarium quickly and easily using the phosphate test kit from Heyl.
Recommended phosphate values:
- Freshwater aquarium (community aquarium): 0-0.4 mg/l
- Malawi Lake Tanganyika aquarium: 0-0.4 mg/l
- Planted aquarium with few fish (aquascaping): 0.1-1.5 mg/l
- marine aquariums: 0-0.1 mg/l
- Ponds: <0.05 mg/l
TESTOVAL® Colour Comparator: ORTHO-PHOSPHAT - Heyl Neomeris Shop
In our main shop Heyl Neomeris Shop as well as our Pocket Tester Shop you will find a large product portfolio of hand testers as well as colour comparison kits, which enable you to analyse the water quality in your aquarium in an uncomplicated and quick way.