The N-Fill Automatic Top Off System is designed for aquarists who want dependable water level stability with built-in redundancy and intelligent safety features. Engineered for both freshwater and saltwater aquariums, N-Fill delivers consistent top-offs while actively protecting against common ATO failures like stuck floats, siphoning, or overfilling. Dual Float Sensor Redundancy Two independent float switches monitor the same water line at all times. If either sensor detects a low water level, the controller immediately initiates a refill. Should one sensor fail, the second continues to function normallyensuring uninterrupted operation and significantly reducing the risk of missed top-offs compared to single-sensor ATO systems. Smart Over-Fill Protection To guard against overfilling, the controller continuously monitors pump runtime. If the pump runs longer than approximately 90 seconds, the system automatically stops filling and triggers an audible alarm along with a solid red Status LED. This controller-based safeguard protects against stuck floats, restricted tubing, or unexpected reservoir behavior. Intuitive Controller with Clear Status Indicators The compact controller features three simple buttons for complete control: Manual Press and hold to run the pump for priming or quick refills; release to stop. Pause Temporarily pauses automatic filling for 30 minutes, ideal during feeding or light maintenance. Stop Disables automatic top-offs for 24 hours during major maintenance or water changes. Three LED indicators provide instant system feedback: Power Confirms the controller is powered and ready Filling Illuminates while water is being added Status Off during normal operation, blinking when paused, and solid red during Stop mode or over-fill alarm Built-In Siphon Protection An included siphon breaker connector and protective cover help prevent gravity siphoning when the reservoir is positioned higher than the aquarium. When paired with the included N-Neon ATO Tubing Organizerwhich keeps the tubing outlet above the water surfacethis adds another critical layer of safety. Quiet, Compact DC Pump The included submersible DC pump is small enough to fit in most common ATO reservoirs while still delivering reliable flow and head pressure for nano and mid-size aquariums. Its quiet operation makes it ideal for living spaces and display tanks. Freshwater & Saltwater Ready Designed for long-term reliability in both freshwater and marine environments, the N-Fill ATO is suitable for planted tanks, reef aquariums, and fish-only systems alike. Electrical Safety You Can Trust The system includes a UL-listed 12 V 1 A power adapter, providing safe, stable power delivery for use around water. Whats Included N-Fill Controller Dual float sensors with adjustable mounting holder N-Neon ATO Tubing Organizer Submersible DC pump Water tubing (2 m / 6.5 ft) Siphon breaker connector with cover UL-listed 12 V 1 A power adapter