Electrical conductivity
Measures the ability of water to conduct electrical current. It indirectly indicates the total quantity of dissolved salts and minerals.
Detailed explanation
Conductivity is closely linked to TDS (Total Dissolved Solids). The more salts and minerals dissolved in the water, the higher the conductivity.
It is measured in microsiemens per centimetre (uS/cm). Pure osmosis water has a conductivity close to zero. Tap water varies from 200 to 800 uS/cm depending on the area. Natural sea water is around 50.000 uS/cm.
In tropical freshwater aquariums, conductivity is a precious tool for understanding the composition of the water without doing dozens of individual tests. Amazonian fish such as Discus, Cardinal and Apistogramma prefer waters with low conductivity (50-200 uS/cm). Malawi African cichlids thrive at higher values (300-800 uS/cm).
For the reproduction of many species, conductivity is a determining factor. Lowering the conductivity by simulating the rainy season can stimulate egg laying in species such as Corydoras.
In marine aquariums, conductivity is used little because the refractometer and hydrometer measure salinity in a more practical way.
In ponds, conductivity helps to understand if there is an excess of dissolved minerals, for example after acid rain or in areas with calcareous soil.
Conductivity metres (conductometers) are inexpensive, easy to use and do not require reagents. A good investment for those who want to monitor water quality without buying dozens of test kits.
Reference values by aquarium type
| Aquarium type | Recommended range |
|---|---|
| Marine (reef) | 48000 - 55000 uS/cmSalinity is usually used instead of conductivity |
| Tropical freshwater | 100 - 600 uS/cmAmazonians: 50-200. African cichlids: 300-800 |
| Coldwater / pond | 200 - 800 uS/cm |
| Brackish | 5000 - 30000 uS/cm |
How it is measured
With a digital conductivity metre (TDS/EC metre). It costs a few euros and is very simple to use. Simply immerse the probe in water and read the value. Calibrate periodically with reference solution.
What happens when it is too low
Indicates water that is too low in minerals. Fish can have osmoregulation problems. Plants can suffer from micronutrient deficiencies.
What happens when it is too high
Excess minerals. Possible osmotic stress for soft water fish. It may indicate accumulation of pollutants between water changes.
Coralia Lab monitors this parameter with AI diagnostics. Tank Score alerts you when a value moves outside the recommended range for your aquarium.
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