Description
Hugo Kamishi Hydrometer
A hydrometer is an essential piece of equipment for anyone with a salt water aquarium.
It allows you to determine the specific gravity of your salt water, this information is therefore really essential for the health of your fish.
The operation of a hydrometer is based on Archimedes’ principle of buoyancy. A solid object, such as a hydrometer, will be buoyed up when placed in a fluid to a degree equal to the weight of the portion of the object suspended below the surface of the liquid. The degree to which the hydrometer is submerged below the surface is therefore an indication of the liquid’s density. As a result Lower density liquids will cause the hydrometer to sink further. The degree of density, which reflects the liquid’s specific gravity, can be read by noting the calibration mark on the stem of the instrument at the fluid’s surface
About salinity
The preferred water for marine and reef tanks is RO/DI water, as it is in a very pure form. The commercial salt mix contains all the salts and minerals needed. Salinity also describes the content of these dissolved salts and minerals in the water and is measured in parts per thousand (ppt).
The easiest and most common instrument to measure the salt concentration in aquarium is the hydrometer. A hydrometer is a device that measures the density or specific gravity of a liquid. The more salt in the water the more dense it is.
Especially relevant is that is important to understand that salinity and specific gravity are related – but not the same.
Salinity can be measured by
(a) boiling down a water sample
(b) measuring conductivity by electronic means,
(c) other laboratory methods which are either too complex or too expensive.
And so finally Specific gravity indicates density, while salinity refers to the actual weight of the salt.
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