When it comes to auto-top-off devices, reliability is king. AVAST Marine Works’ ATO Kit is one intelligently designed top-off device.  Unlike most ATO sensors mounted with suction cups or brackets, its direct magnet-mount allows for secure placement – an extremely important performance criteria for water level sensors.  Using a pressure-sensitive switch, AVAST’s ATO Kit “is capable of maintaining the sump water level within +/- 1/4″ tolerance (1/2″ overall) and features a built-in range buffer or hysteresis effect, which prevents rapid on-off switching that sometimes occurs when cheap float switches bob up and down in small waves.”

AVAST Marine Works has now added two new optional features to their ATO Kit, further improving its functionality and reliability.

♦ Digital I/O versions now have four specific aquarium controller compatibility options (Neptune, Profilux, Reef Angel, Digital Aquatics) as well as a bare-wire version that can be tied in to an existing breakout-box or similar existing input terminal block.

♦ All versions now have the ability to add a backup shutoff float valve in case something goes wrong with the controller or outlet switch/connection.

As before, the magnet mount includes a handy ATO-tube holder fitting (which swaps out for the float).

Details here:
http://www.avastmarine.com/ssc/do/product/rigging/Top-off-Kit

The backup shutoff float valve is a $15 option … a small price to pay for peace of mind.  Take it from a victim of an ATO “gone wild””: Safeties and redundancies are highly recommended.

Technical Data:
Water level sensitivity: 1/2″
Magnet strength: up to 1/2″ glass
Magnet bracket dimensions: 2-5/8″ x 2-5/8″
Switch box dimensions: 4″ x 2.25″
Input power: AC 110v
Relay box capacity: 3 amps
Switch rating: 10+ million cycles
Warranty: 1 year
Made in the USA

(Above): The ATO Kit with optional backup safety float valve.