TMC floating Hydrometer/Thermometer
With this hydrometer and thermometer you can track both the temperature and the salt levels in your marine aquarium and not need two pieces of equipment to do it.
You just need to gently lower this hydrometer into your aquarium water, the hydrometer will need to float freely without being in contact with any surface and a reading can then be taken at the level which the hydrometer breaks the surface.
This will give you your salinity reading with an accuracy of 0.002.
The thermometer gives you an accurate temperature reading, ensuring that the water temperature is correct for the live stock in the tank, this simulates their natural environment.