Things You'll Need
- Hydrometer
- Saltwater aquarium
- Flat surface
Instructions
Rinse your hydrometer out with tap water.
Dip the hydrometer into the aquarium and fill with water from approximately 6 inches beneath the surface.
Pour out excess water until it reaches the fill-to line on your hydrometer.
Tap the hydrometer once gently on a flat surface to remove air bubbles from inside.
Place the hydrometer on a flat surface and wait five seconds.
Read the hydrometer by looking at where the "arm" or "needle" stops in the number range.