color as shown Size9*12*3cm Weight:200gramm How to use1. Insert the hydrometer 15 cm below the surface of the water tank or fish pond until the water overflows the baffle. 2. When the water reaches its maximum level, remove the hydrometer and keep it from lying on a flat surface. 3. If bubbles are attached to the pointer, the degree will be inaccurate. If bubbles appear, gently tap the hydrometer to shake off the attached bubbles. Note for useBefore using the hydrometer for the first time, you must clean the oil stains on the inner surface to improve accuracy. It should also be cleaned after measurement, because if salt crystallizes in the hydrometer, it will affect the accuracy of the degree. It is recommended that the proportion of sea water in the sea pool should be between 1.020 and 1.023. How to cleanIf there are salt crystals in the hydrometer, do so soak in warm water or vinegar for 30 minutes, then rinse it with water. Good Features It can reach 15cm (6 inches) deep in the surface of the bottle. water to avoid errors caused by inhaling the oil film on the water surface. It is necessary to keep hands clean during measurement or use measuring tools to avoid contamination of seawater in the fish pond. The accuracy of our hydrometer can reach +(-)0.001 specific gravity units. Suitable forSuitable for brackish and marine aquariums. Perfect for testing both the salinity and specific gravity of your brackish and marine tanks. And each hydrometer has a laser engraved patent number.