NOTE: The specific gravity is temperature dependent. With increasing temperature the specific gravity decreases. Therefore, the measured water temperature should be 25 °C / 77 °F to obtain a correct result.
- Fill the measuring cylinder with maximum 400 ml saltwater (water temperature = 25 ° C / 77 °F).
- The hydrometer should be dry and clean.
- Gently place the hydrometer into the water until it floats freely.
- Now read the specific gravity on the blue part of the scale of the hydrometer at the level of the water surface - NOT at the level of the meniscus, which is creeping higher at the edges!
- To avoid any distortion of future measurements, rinse the measuring cylinder well with fresh tap or reverse osmosis water to remove salt residues after each use.
DO NOT CONFUSE: The “Tropic Marin® ARÄOMETER”, which is used in German speaking countries, has a scale with a green printing and the indication ‘Dichte/density’.
We recommend different salinities for various tank types:
Tank type | Specific gravity at 25 °C / 77 °F | Salinity in ‰ (psu) |
---|
Fish only tanks (no invertebrates) | 1.023 - 1.025 | approx. 31 - 33 |
Reef tanks | 1.025 - 1.026 | approx. 33 - 35 |
Shrimps | 1.026 - 1.027 | approx. 35 - 36 |