Specification: Item Type: Aquarium Salinity Tester Material: Plastic Application: Aquarium Seawater Concentration Meter Specific Gravity Range: 1.000-1.030 Salinity Range: 0-40 Applicable Temperature: 20-30? / 68-86? How to Use: 1. Insert the hydrometer to 15cm (5.9in) below the water of the water tank or fish pond until the water overflows the baffle (slowly fill with water to prevent the upper air bubbles from adhering to the pointer). 2. When the water is full (level with the top of the baffle), take out the hydrometer and place it on a level . 3. Air bubbles adhering to the pointer will cause inaccurate readings. Carefully tap the hydrometer to shake out the adhering air bubbles. 4. Read the specific gravity according to the inner scale, and read the salinity (PPT) according to the outer scale. It is recommended that the specific gravity of the seawater in the seafood pool is between 1.020-1.023, that is, within the line. 5. Rinse with water after each use. Package List: 1 x Aquarium Salinity Tester 1 x Plastic Rod Note: Before using the hydrometer for the first time, fill it with warm water and detergent to the oil stains inside, which can be more accurate.