The CoralVue Hydros Triple Optical Auto Top-Off ATO Kit is an essential accessory designed to seamlessly integrate with your existing CoralVue Hydros Control 2, Control 4, Control X2, or Control X4 device, transforming it into a precise and reliable automatic top-off system. This kit works to consistently maintain stable water levels in your saltwater aquarium by replenishing evaporated water with fresh RODI water, preventing salinity fluctuations that can stress corals and fish. It is not a standalone system and requires a Hydros controller for operation. This advanced ATO kit features a triple water level sensor, offering enhanced safety and redundancy to prevent overflows or dry pumps. The primary optical sensor is remarkably compact, just over half an inch thick and the size of a US penny, with no moving parts to fail. It magnetically mounts to most clear, tinted, or painted surfaces up to half an inch thick. The kit includes a Hydros Triple Water Level Sensor, a Hydros DC Micro Pump, a hang-on tubing mount, 80 inches of tubing (8.5mm OD - 6.5mm ID), and a siphon break for a complete setup. The Hydros Triple Optical Auto Top-Off Kit is ideal for reef aquarists who already own a CoralVue Hydros controller and wish to leverage its capabilities for automated water level management. It is particularly well-suited for small aquariums or all-in-one tank setups where water level stability is crucial but fluctuations are minimal. By utilizing your existing Hydros system, this kit provides an efficient and cost-effective solution for precise water top-off without the need for a separate, dedicated ATO unit.