The new aquarium hobbyist has many challenges, but none is more annoying than the chore of adding water, every day, to make up for that lost to evaporation (a.k.a. topping off/up). This alone usually makes the automatic top-off (ATO) device the first piece of automation equipment purchased. The ironic flip side of this decision is that a faulty ATO device is one of the leading reasons for catastrophic aquarium failure, or even worse, flooding of the house or business. Not all ATO devices are created equal. Sadly, many ATO on the market are made with cheap components, have very little protection against these catastrophes, and are just a nightmare to assemble and install correctly. Three Levels of Security 1. Backup Optical Sensor - Should the main water level sensor fail, this second optical sensor is the backup. If water continues past the primary sensor, and then covers this one, the pump will be shut off and an alarm will sound. 2. IQ-Fill - Water run-time intelligence - If both the primary water sensor AND the backup optical sensor fail, the algorithm used in the ATK will not add more than double the learned water amount. It will shut itself off and sound an alarm. 3. Physical float valve - the final backstop If for some reason all the electronic fail safes do not work, and water is continuing to be sent to the aquarium, the mechanical float valve is the safety device that will stop the water and prevent death to your aquarium and water on your floor. The ATK Includes: FMM - Fluid Monitoring Module (runs standalone) Pre-assembled water level mechanism with: Magnetic acrylic mount (works up to 1/4″ glass/acrylic) Two (2) optical water level sensors Float valve 90 degree tubing fitting PMUP ATO Pump 24V 36W power supply 4m of orange RO tubing 3/8″ -> 1/4″ push-fit adapter fitting 1/4″ -> 1/4″ push-fit siphon break Set-screw for non-float-valve applications