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Auto Top Off

Auto Top Off

92 reviews
$ 99.99

Finally, a top-off control sensor that is mounted to your sump with a magnet rather than a clunky bracket!  Driven by a pressure-sensitive switch located in the relay box, a strong magnetic field won't affect its operation.  The sensor tube can't get clogged with calcium deposits or activated by wayward snails as there are no moving parts.  Our top-off system 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.  The magnet bracket is capable of holding on up to 1/2" thick glass.  The slim design relay box is unobtrusive and can handle up to a 3 amp pump at 110v AC.  The green LED light indicates when the circuit is active and the pump is running.

The magnetic bracket also contains both an adjustable 1/4" to 1/2" fitting, useful for holding the tube from your top-off pump in place.  This fitting can be switched out for an optional backup mechanical float valve, which will physically close and stop the flow from your pump in the event of an electrical or switch issue.  

Our digital output version is now available for use with most aquarium controllers.  This version is designed without an outlet; just plug the ATO pump into your controller's relay box and set up the controller to read the pressure switch state (see instruction manual for details).  It is available with the plug types of several popular aquarium controllers.  For example, Neptune Apex uses a "minidin-8" style plug.  To use this, simply plug into the port marked "I/O" on the controller, and program according to instructions.  If you already have something plugged in to that port, you will want to use their Breakout Box and select the "bare wire" option below.  See instruction manual for further details. Bare wire connection is 2 strand, non-polarized 22 AWG shielded wire. In the case of ReefKeeper Lite/Elite, use this option with the float switch adapter wire that came with your controller and/or SW5 Switch Module.

Cerebra, Reef Angel, and RKL/RKE compatible plugs are also available.
The Digital Output version allows several non-standard uses for this switch. For example, it can be a low level sensor in your sump that is impervious to coralline algae and snails, can turn off your return pump and send you a text message at the same time. There are a lot of options since you can reverse the logic of the switch at the controller.

Our switch and all components are made in the USA. 

Technical Data:

Water level sensitivity: 1/2" 
Magnet strength: up to 1/2" glass
Magnet bracket dimensions: 1-3/4" front to back x 2-1/4" wide (excluding external magnet half, 1/2" thick)
Switch box dimensions: 4" x 2.25" 
Input power: AC 110v
Relay box capacity: 3 amps
Switch rating: 10+ million cycles
Warranty: 1 year

Click here for Standard outlet box ATO installation manual
Click here for Digital output ATO installation manual

Click here for ATO and related Pressure Switch troubleshooting guide

Customer Reviews
4.9 Based on 92 Reviews
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Eric B.
United States United States

Love the simple design and use of a pressure switch instead of optical like most of the others.

Hans H.
United States United States
Simple, Rock Solid, well made.

I've got a pair of the digital version of these ATO water sensors connected to my Profilux 4. With no moving parts to get crusted up, no narrow ports to clog up, or optical sensors to get otherwise confused, I'm finding them to be just rock-solid. Connection into my Profilux was super simple, as is adjusting the level either through the magnetic mount, or adjusting the height of the sensor tube in the mount.

Ryan R.
United States United States

Wasn’t the best experience. The ato showed up with no directions. It was the version that doesn’t have a power supply and plugs directly into apex. I reached out to avast and they quickly sent me a link to install. However the Indo had zero Input in how to program the on/off value. Not to mention I ordered a probe holder that broke when I tried to put the pressure switch/probe into it because of how tight of a fit it is.

Avast Marine Works

Sorry to hear about your experience. We are happy to walk you through the setup and of course will replace anything that was broken. Please reach out to so we can make this right.

Paige M.
United States United States
Reliable auto top off

Installation was somewhat difficult because the instructions were sketchy and my unfamiliarity with Apex system. But it has been reliable ever since.

Roshan P.
United States United States
Didn't include pressure sensor in package

Had to wait about 2 extra weeks to get my ATO setup since they didn't include a pressure sensor in the package. Quality otherwise seems good.