Water naturally evaporates from your aquarium and needs to be replaced regularly. When topping off your tank, always use prefiltered water—either reverse osmosis (RO) water or properly conditioned freshwater. Since salt does not evaporate, it’s important to check your specific gravity with a hydrometer to ensure your salt levels remain balanced. If the specific gravity is lower than desired, instead of adding freshwater, use premixed saltwater to restore the correct salinity.

Most hobbyists rely on plastic aquarium hydrometers with swing arms to measure specific gravity accurately. One excellent option is the Full Range Hydrometer, which provides precise readings for both saltwater and reef aquariums. However, many hobbyists neglect regular maintenance. Over time, the swing arm or pointer can accumulate deposits, affecting readings. To maintain accuracy, rinse the hydrometer in freshwater after each use. For a deeper clean, soak it in vinegar (a mild acid) for about 30 minutes, then rinse thoroughly. This simple step ensures reliable readings for years to come.

And while you're fine-tuning your water parameters, don’t forget to check your filtration setup! A well-maintained filtration system is key to keeping your aquarium water clean and healthy. Whether you're upgrading or just performing routine maintenance, investing in the right filtration materials will help maintain a thriving aquatic environment.