Hydrometers for Aquariums

There are two basic types of hydrometer. A swing arm hydrometer is a small box that holds water. Inside the box is an arm that rises in the water according to the specific gravity. The swing arm points to a specific gravity chart on the box, which indicates the salinity level. A glass hydrometer is a tube that floats in the water sample, with the specific gravity chart printed on the hydrometer. The water level at which the hydrometer floats indicates the specific gravity.

A fish tank hydrometer is less expensive than a refractometer, but also less precise. A glass hydrometer is useful to have on hand as a reference and backup to the refractometer.
2 Results
Coralife Deep Six Hydrometer Wide Range Specific Gravity Meter

Coralife Deep Six Hydrometer Wide Range Specific Gravity Meter

Fluval Sea Hydrometer

Fluval Sea Hydrometer

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