Hydrometer
Proper salt content is vital to the health and well being of captive marine species. The amount of salt in the water affect specific gravity, which is acceptable at approximate level between 1.020 and 1.025. Salinity of the water within this level is the safest for marine species. When salinity is higher, it is recommended to add fresh water to the tank. In case of a low level of salinity, saltwater mix should be added to increase the specific gravity of water. Saltwater hydrometers are direct-reading instruments that indicate specific gravity of the water in aquarium at a particular temperature. |
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Thermometer
The temperature of a saltwater tank varies depending on the type of marine species:
- For tropical fish: from 70F (21C) to 80F (27C) with 75 being a midpoint.
- For fresh water fish: from 60F (15C) to 70F (21C) with 65F (18C) recommended.
- For lobster and crabs: from 42F (5C) to 50F (10C) with 46F (7.5C) as an optimum temperature.
Wild temperature variations increase stress and mortality of animals. Specific gravity is temperature dependent. When the water temperature rises, the specific gravity will fall roughly by .001 for every 10 degrees. Check salinity and temperature of the water daily.
Instructions:
Place a sample of aquarium water in a clean tall glass or jar that is deep enough to float the hydrometer freely within. Specific gravity is determined by reading the line in the unit closest to the water surface level. Read the thermometer in the higher unit; to ensure the water temperature is consistent and safe for your marine inhabitants. The function of the hydrometer is based on Archimedes finding that “a force equal to the weight of the liquid displaced will buoy up a solid suspended in a liquid.” Thus, the lower the density of the substance, the lower the hydrometer will sink. |
