Neptune ATK Auto Top-Off Kit - Version 2 Neptune ATK Auto Top-Off Kit - Version 2 is a premium automatic top-off system for replacing aquarium water lost to evaporation, with standalone operation, Apex expansion, Version 2 optical sensors, PMUP V2 pumping, and multiple layers of overfill protection. ATK v2 Auto Top-Off for Stable Aquarium Salinity Evaporation removes freshwater from an aquarium while leaving salt and minerals behind, which can cause salinity to rise in marine and reef systems. The Neptune ATK Auto Top-Off Kit - Version 2 helps solve that daily maintenance problem by automatically adding freshwater from a reservoir when the aquarium or sump water level drops. What makes the ATK v2 especially valuable is the way it combines convenience with protection. Instead of relying on a single float switch, the system uses improved optical sensors, a mechanical float valve, IQ-Fill runtime intelligence, an audible alarm, and the included FMM module to create a more secure top-off system for reef, saltwater, and freshwater aquariums. Neptune ATK v2 Features Complete automatic top-off kit: Includes the FMM module, PMUP ATO Pump Version 2, water-level sensor assembly, power supply, tubing, fittings, siphon break, and setup hardware needed for a complete ATO installation. Works without an Apex: The included FMM module can run the ATK as a standalone top-off system, making it useful even on aquariums without a full Apex controller. Apex expansion ready: When connected to a compatible Apex system, additional monitoring, alerts, logging, and control options become available through Apex Fusion. Improved Version 2 optical sensors: Two optical water-level sensors provide electronic level detection with no traditional moving float-switch mechanism for the primary sensing function. Backup mechanical float valve: The integrated float valve adds a physical safety layer to help protect against overfilling if an electronic control issue occurs. IQ-Fill runtime intelligence: Learns the normal top-off runtime pattern and helps limit abnormal pump operation that could otherwise lead to overfilling. PMUP ATO Pump Version 2 included: Uses Neptune's compact 24VDC PMUP V2 utility pump for controlled freshwater delivery from the top-off reservoir. Audible failure alarm: Built-in alarm capability helps draw attention to top-off problems even when the system is being used in standalone mode. Pre-assembled sensor mechanism: The water-level mechanism arrives with the magnetic mount, two optical sensors, float valve, and tubing fitting already assembled for easier setup. Accessory expansion through FMM: The included FMM has additional ports that can be used with compatible FMM accessories when the system is configured appropriately. Official Neptune ATK v2 Product Video Why Redundant ATO Protection Matters Automatic top-off systems are convenient, but a poorly protected ATO can create serious problems if it sticks on, runs too long, siphons, or adds too much freshwater. That can flood the area around the aquarium, dilute salinity, stress livestock, and disrupt reef chemistry. The ATK v2 is designed around layered protection so one issue is less likely to become a major failure. The lower optical sensor handles the normal top-off trigger, the upper optical sensor acts as an electronic backup, the float valve provides a physical shutoff, the siphon break helps prevent unwanted back-siphon behaviour, and IQ-Fill limits abnormal runtime. Together, these features make the ATK v2 a strong choice for hobbyists who want automated freshwater replacement without treating ATO safety as an afterthought. ATK Auto Top-Off Kit Specifications Product type: Automatic top-off system Version: Version 2 Operation: Standalone or Apex-connected Module included: FMM Fluid Monitoring Module Pump included: PMUP ATO Pump Version 2 Water-level sensors: Two optical water-level sensors Version 2 Backup shutoff: Mechanical float valve Mount type: Magnetic acrylic mount Mount compatibility: Works up to 1/4" glass or acrylic Power supply: 24V 36W power supply included Tubing included: 4 m orange RO tubing Included fittings: 90 degree tubing fitting, 3/8" push-fit adapter fitting, and 1/4" push-fit siphon break Primary use: Replacing evaporated freshwater in aquarium systems Standalone and Apex-Connected Use The ATK v2 can run as a standalone ATO, which makes it accessible for aquariums that do not currently have a full Apex system. In standalone use, the FMM controls the top-off process, sensors, pump, and alarm logic. This makes the kit useful for many hobbyists who want a premium ATO without committing to a larger controller system immediately. When connected to a compatible Apex system, the ATK v2 becomes part of a broader aquarium monitoring and control platform. Apex users can take advantage of additional status visibility, notifications, logging, and more advanced programming options depending on the system and accessories connected. Installation and Compatibility Notes Install the ATK in a sump or aquarium area where the water level changes from evaporation. Use only freshwater top-off water appropriate for the aquarium, and position the reservoir, tubing, siphon break, and discharge point so the system cannot siphon unexpectedly. The magnetic mount is designed for glass or acrylic up to 1/4" thick. As with any ATO, placement matters. Keep the freshwater reservoir volume appropriate for the system, inspect the optical sensors regularly, keep the PMUP intake clean, and test the top-off cycle before relying on the system unattended. Avoid placing sensors where bubbles, splashing, snails, algae buildup, or equipment turbulence can interfere with reliable level detection. Setup Directions Mount the pre-assembled water-level mechanism at the desired operating level, place the PMUP V2 in the freshwater reservoir, connect the orange RO tubing and siphon break, then connect the pump and sensors to the FMM module. Power the system using the included 24V 36W supply and complete the standalone or Apex setup process. Test normal fill behaviour, backup sensor response, float valve shutoff, siphon-break placement, alarm function, and reservoir routing before leaving the top-off system unattended. What's Included FMM Fluid Monitoring Module Pre-assembled water level mechanism Magnetic acrylic mount Two optical water level sensors Version 2 Float valve 90 degree tubing fitting PMUP ATO Pump Version 2 24V 36W power supply 4 m orange RO tubing 3/8" push-fit adapter fitting 1/4" push-fit siphon break Set-screw for non-float-valve applications
