by Andy Horton
A Hydrometer is an essential item of equipment for measuring the specific gravity, and hence calculating the salinity of the water. There are 2 types available.
If the bulbous hydrometer is used, it should be placed in the aquarium water when the filtration is turned off, and the reading taken at the water surface level.
The specific gravity of water is
denser at lower temperatures, and the reading on the hydrometer scale (calibrated
at 15° C ) at the meniscus (curved upped
edge of the liquid where it meets the stem) will be correspondingly higher
as shown below:
|10C - 80C||1.027|
|90C - 130C||1.026|
|140C - 180C||1.025|
|190C - 240C||1.024|
For a greater range for brackish
water studies, please consult
Starfish and urchins are intolerant of salinity alterations
Synthetic marine salts should not
be mixed in an inhabited aquarium. A fermentation bin, used in beer making
is an ideal container for mixing the salts prior to changing a 20% maximum
proportion of the water.
Seawater for the Aquarium
Wet Thumb (Marine Aquaria page)