Ways to measure salinity of water | Blog about aquariums | Resources | Aquaforest

Why is measuring salinity of water so important?

Testing water parameters is an integral part of maintaining a marine aquarium. Knowledge about the chemical composition of water allows us to diagnose emerging problems and resolve them easily. While not every parameter can be tested at home, it is worth regularly checking at least the most basic ones, such as water salinity.

Just like in nature, maintaining appropriate and stable salinity level in a marine aquarium is crucial for the health and well-being of aquatic organisms. Generally, it should be around 35 ppt (parts per thousand) for reef tanks or 33 ppt for fish-only tanks.

Ways to measure the salinity of water

There are many methods for measuring water salinity level. We can choose from various options such as hydrometers, refractometers, or digital salinity meters, each differing in usage and accuracy.

Hydrometer

The first solution is the hydrometer, a simple tool that resembles a thermometer. It works by submerging it into a prepared water sample, measuring its density. The hydrometer will sink more or less depending on the salinity value, and the result is read from the scale on the instrument. While easy to use and relatively cheap, its readings may not always be accurate enough.

Refractometer

The second option is the refractometer, which is the most popular tool among marine aquarists. It is used by placing a few drops of water on a prepared glass slide and looking through the eyepiece. The principle behind its operation is that water with different salt concentrations refracts light at different angles. This way, the aquarist obtains reliable and accurate salinity readings. There are also digital refractometers, which are much easier to use. They allow for more convenient salinity measurement, without the need for strong light, and the result is displayed clearly on a screen. However, both types of refractometers require calibration before each use.

Digital Salinity Meters

Digital salinity meters are the most convenient devices for measuring salinity. They operate based on the electrical conductivity of the water and offer the highest measurement accuracy. Additionally, they are very easy to use compared to other methods. Simply immerse the tip of the meter into the water sample, and the result is instantly displayed on the screen. Unlike refractometers, digital meters require less frequent calibration, and the measurement process is much quicker.

When choosing salinity measuring equipment, we should ensure that it is specifically designed for marine aquariums. Many refractometers available for purchase are meant for the food industry, not for aquariums. These instruments are calibrated to measure parameters different from marine salinity, which can lead to inaccurate readings when used in saltwater. The main difference lies in the measurement range and how the refractometer interprets the refraction of light through various dissolved substances. Using one of these for a marine aquarium can result in incorrect readings, leading to improper aquarium management. To avoid errors, always use refractometers designed specifically for saltwater, with the appropriate scale and calibration.

Optimal Temperature to test the salinity of water

The temperature of the water sample is crucial. Water density changes depending on the temperature, which affects the salinity reading. Therefore, before testing, we should ensure that the sample has the optimal temperature. It is generally assumed that the optimal temperature for salinity measurement is around 25°C. Refractometers and other devices are calibrated to provide measurements closest to reality at this temperature. However, if the water temperature differs, it is necessary to use correction tables or calibrate the devices according to the temperature in the aquarium.

When to measure salinity level?

Daily monitoring

Regular testing of at least the basic water parameters in a marine aquarium should be a good habit for every aquarist. Staying informed about the aquarium’s status makes maintenance easier and allows for a quick response to any issues. Daily salinity checks, especially in small tanks, are important to prevent unforeseen fluctuations that could harm the tank’s inhabitants. When water evaporates, the salts remain in the tank, causing an increase in salinity. It’s important to remember that replenishing evaporated water should only be done with reverse osmosis or distilled water to avoid further salinity increases.

After Water Changes

Water changes are a key task for aquarists. They help remove excess harmful substances and replenish compounds constantly consumed by corals. Therefore, it’s crucial to prepare fresh saltwater with the same salinity as the aquarium. It is also advisable to check the salt level after a water change to ensure that no significant changes have occurred in the aquarium’s parameters.

When Introducing

New Life to the Aquarium Shopping for new tank inhabitants is the most enjoyable part of maintaining an aquarium. Introducing new life into the tank is exciting, but it’s important to stay calm and take a careful approach. First, check the salinity of the water the new coral, anemone, crab, or fish was transported in. If it differs from the salinity of your tank, perform a drip acclimation, periodically testing the salinity of the water the organism is in.

Crisis Situations

If you notice unusual behavior in the aquatic organisms or cloudiness or discoloration of the water, your first action should be to test the basic parameters, including salinity. It’s important not to react too quickly if any deviations are detected. Returning to the target parameters should be done gradually, as a sudden change could further harm the already stressed reef.

Maintaining consistent salinity is one of the keys to success in running a marine aquarium. It’s not difficult, but it requires regular attention. Therefore, it is worth regularly testing key water parameters and choosing the most accurate solution for this task. Developing the habit of regular water parameter monitoring will undoubtedly benefit the tank’s health, making it worth spending a few minutes a day to know as much as possible about your aquarium.