Sera Marin Hydrometer

For the uncomplicated monitoring of marine water density

The salinity (salt contents) can be deduced from the measured density.

Since the salinity of marine water in an aquarium must be kept constant, the aquarium water should regularly be checked accordingly. The water to be tested is filled into a sufficiently tall water glass, and the scale of the immersed hydrometer is read off on according to its immersion depth.

Getting accurate readings

Most marine aquarists aim for a specific gravity of roughly 1.023 to 1.026, with reef tanks usually kept towards the upper end. Density changes with temperature, so always test water at the tank’s normal temperature and check the leaflet for how the scale should be read. Before reading, tap the glass gently to free any air bubbles clinging to the hydrometer, which would make it float higher, and read the scale at eye level. When the reading creeps up between water changes, it is usually because water has evaporated while the salt stays behind, so top up with fresh, purified water rather than saltwater. Test newly mixed saltwater before every water change too. Rinse the hydrometer in fresh water after use so salt crust does not build up and affect later readings.

Sera Marin Hydrometer specifications

• Brand: Sera
• Brand website: sera.de
• Product: Sera Marin Hydrometer
• Category: Fish Water Care