The Neptune Magnetic Optical Sensor is a modern, compact device designed for precise water level monitoring in saltwater aquariums. This versatile sensor plugs directly into an Apex FMM port, utilizing reflected infrared light to accurately detect changes in water level, signaling your Apex controller when it transitions between wet and dry states. It is an essential component for building custom auto-top-off (ATO) systems, serving as a critical high-level warning sensor in sumps, or monitoring water storage levels for various aquarium applications.

Featuring an improved look, feel, and design, this sensor replaces the previous OS-1-M, offering an updated form factor that fits into tighter spaces and enhances protection against water incursion. It ensures precise water level control with its completely waterproof construction and built-in magnetic mount, complemented by a silicone-encased external magnet. The strong magnetic mount is suitable for securely attaching to glass or acrylic up to 1/2 inch thick, providing robust and reliable placement.

This product is ideal for any reef aquarist leveraging the power of an Apex controller who requires dependable and accurate water level detection. It is particularly beneficial for those looking to implement a DIY auto-top-off system, seeking an extra layer of protection against overflows in their sump, or needing to monitor the levels of their RO/DI water reservoirs. Its compact design and strong magnetic attachment offer exceptional versatility and ease of integration into diverse aquarium setups.