The ATK is hard programmed at the factory so that it will alarm if the upper backup sensor is submerged for more than 10 min (might be 15, I'm not positive.) Any alarm requires a hard reset by unplugging the device. (This also erases the IQ fill memory.)
If you turn of your pump to feed and the water level rises high enough then you will get an alarm. This was one of my main complaints with the ATK.
You can get a mount and move the backup sensor higher which would fix that problem. (The Tunze lets you mount the backup sensor separately by default.)
The other potential issue with the ATK is that the IQ Fill protection function will shut it off and cause an alarm if the pump runs for more than 3x the average run time. With my bean animal overflow system, the water level in the return chamber drops at startup, causing the ATO to kick in. The time it needs to start up and stabilize is long enough that it causes the IQ Fill function to alarm. Your system my be different, but this is something to consider.
If you're planning on getting a Neptune Apex in the future, then the ATK makes sense. Otherwise I'd recommend the Tunze for about the same cost. It has a bullet proof history, many of the same safety features implemented slightly differently and is more convenient to use IME
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