Features: 1.Automatic Detection: The seawater hydrometer can be read inside and outside of fish pond and tanks and automatically detects the specific gravity of water samples. 2.Easy to Operate: The seawater densimeter is used at a depth of 15cm (6 inches) to avoid errors caused by inhaling the oil film on the water surface. 3.Keeps Clean: Keeping your hands clean when using the aquaculture seawater densimeter will prevent contamination of the seawater in the fish pond. 4.Accurate Readings: The ocean hydrometer is easy to read and accurate to 0.002 specific gravity units and gives accurate readings in fish pond at temperatures between 20?30C. 5.Safe Material: Sealevel automatic hydrometer is made of high quality transparent plastic material, accurate, durable, and easy to read your marine aquarium's salt level and specific gravity. Specification: Item Type: Seawater Hydrometer Material: Plastic Use: Aquarium, Aquaculture Seawater Concentration Meter PackageList: 1 x SeawaterHydrometer Note If salt crystallises on the pointer, this can lead to inaccurate readings. If salt crystallises in the hydrometer, soak the hydrometer in warm water or vinegar for 30 minutes, then rinse with water and air dry.