It is very essential to maintain the level of salt and water to keep your Aquamarine species live and healthy. The water from the aquarium evaporates and leaves behind salt. To compensate the level of evaporated water and to know the exact salinity of water Hydrometer is required. The salt water fish is very sensitive and succumb even for the slightest change in the salinity of the water.
Mostly two types of hydrometer are used by the aquarists, the first one comes with a tube and a separate needle about 3/8 in diameter. The sea water is put into the tube and the needle in the sea water. The needles have graduations on the side. By keeping the eyes at the same levels as the seawater in the tube the specific gravity can be obtained.
But care should be taken while calculating SG, it is important to see the needle is not resting on the side of the tube and the needles should not have bubbles attached to it, as this will not provide exact reading.
The other one is swing needle hydrometer. This hydrometer is compact with all the parts are together. The needle is placed in a narrow plastic container. When the container is filled with sea water the needle starts moving in an arc on the graduation marked on the container and stops at the relevant SG. To get the correct reading there should not be any bubbles if there are any gently tap the needle with pencil.
The reading is influenced by the temperature of sea water within them. So reading should be taken immediately the moment you take out sea water. This is true to both the hydrometers. These hydrometers have been designed to operate at the temperature of 75 degrees and if the temperature varies at greater degree refer to the chart that is made available with the hydrometer that helps you to make corrections.
