Coralife Deep Six Hydrometer Coralife Deep Six Hydrometer is a marine aquarium salinity and specific gravity meter for checking saltwater concentration in reef and fish-only systems. It provides easy-to-read specific gravity and salinity scales with a bubble-resistant design for more reliable readings. Marine Salinity Testing for Reef and Fish-Only Aquariums The Deep Six Hydrometer is designed for routine saltwater aquarium maintenance where salinity stability matters. Its redesigned body, integrated bubble diffuser, and stable base make it easier to collect and read a sample without needing a separate test cylinder. Bubble-Resistant Specific Gravity Meter Features Hydrometer for measuring marine aquarium salinity and specific gravity. Easy-to-read scale with clear markings. Accurate to ±0.001 specific gravity units. Bubble-resistant design helps reduce microbubble reading errors. Calibrated for warm aquariums from 68-85°F or 20-30°C. Built-in base allows the unit to stand on a flat surface for hands-free testing. Coralife Deep Six Hydrometer Specifications Product type: Aquarium hydrometer. Use: Marine, saltwater, and reef aquariums. Accuracy: ±0.001 specific gravity units. Calibration range: 68-85°F or 20-30°C. Dimensions: 5.5" x 1" x 8.7". Readout: Specific gravity and salinity scale. Reading and Rinsing the Deep Six Hydrometer Rinse the hydrometer with fresh water before first use and after each test. Fill the unit with aquarium water, then tap gently to dislodge any bubbles from the swing arm before reading. Use the hydrometer at the appropriate warm-aquarium temperature range and read the scale on a level surface. For best consistency, rinse after use and allow the hydrometer to dry before storage. What's Included One Coralife Deep Six Hydrometer.