Salinity and Specific Gravity

Remember our saltwater aquarium needs to copy the natural seawater as close as possible, this is where we look at salinity and specific gravity. So we need to measure the amount of salt in our aquarium is correct.

Salinity is the actual concentration of dissolved ion in the water and is not affected by temperature. It is measured in parts per thousand (ppt).

But to directly measure it, we need an to buy equipment which is pretty expensive.

There is an easier and more practical way to measure the salt level in your aquarium however. It is by measuring or estimating specific gravity with a hydrometer.

Specific gravity is defined as the ratio of densities of saltwater to pure water at various temperatures. Since it is directly related to water temperature, the hydrometer may not be calibrated to the temperature in your aquarium.

Most hydrometers are calibrated at 60°F. So the reading result still needs to be converted to get the actual or true specific gravity of the water. There should be a conversion table included with the instructions that come with your hydrometer.

At temperatures 75°F - 79°F (standard aquarium temperature), the conversion results in the addition of 0.002 to the reading.

For example, if the reading is at 1.023 and the aquarium temperature is at 77°F, the actual specific gravity of the aquarium water is 1.025.

The normal range should be at 1.012 to 1.024. It should also be maintained at a specific level within this range.

Remember that even a minor fluctuation can cause problems for your aquarium inhabitants.

Here are kinds of hydrometers and more information about each of them.

When salt level fluctuates....

Evaporation is the main cause of salt level change. When the water evaporates in a saltwater aquarium, the salts don't. When this happens, salinity and specific gravity will increases.

Monitoring the water in your aquarium is a must. By doing this you can avoid major fluctuation and resolve the problem right away.

Complete guide to maintenance and care of your saltwater aquarium

Text and Photo Source: Saltwater Aquarium Online Guide