Aquarium: Thermometer & Hydrometer Wide Range Specific Gravity Meter For Marine Aquarium Use. Dry Hands design avoids contamination of aquarium or water sample. Takes a more true water sample at a 6 inch depth avoiding inaccurate surface sampling. Accurate to 0.001 specific gravity & salinity (PPT) measurements. Auto-temperature correcting design. Durable construction for extended life. Designed to give a temperature-corrected reading in warm water aquariums - 68°F to 85°F (20°C to 30°C). Readings can be taken by holding the meter inside the aquarium by the self-leveling hanging device or by taking the meter out of the aquarium and placing on a level surface. Automatically collects perfect sample size by leveling off sample at top of dam. Self-leveling, hanging device included. Proven design offering the ultimate in accuracy for more than a decade.