Hydor auto top off system opinions?


New member
Saw a video on youtube about this auto top off system, it seems like a complete setup, seems well made, they claim the sensors wont be affected by waves and bacterial slime and such. Does anyone have one? how do the sensors work? Lets here some feedback on it!


New member
been running it for about a month now and love it. Set it and forget it...unless the sound alarms go off which are convenient


Active member
It uses conductivity probes.

Are we talking about the same one?


Hydor Smart Level Control ATO System

Simply insert the probe into the aquarium or sump at the desired level. The sensor uses temperature differentials to accurately determine the water level and turns on/off a top off pump accordingly.


New member

So this works on temperature differentials. Would this work if you use to fill up your fresh water reservoir? Two issues come to mind
1) Water reservoir might be the same temperature as the ambient air since you're not heating the water at all or
2) Water reservoir might be colder than the ambient air not warmer, not sure if it just works on the principle of a temperature differential or if the water one must be warmer.


New member
May have a bum unit but I've had it twice stay in low alarm mode without the pump actuating. It knows the water level is low but can't do anything about it. Tried unplugging the unit to restart and the issue remains. Jury is out on this unit for the moment. Worked fine for two weeks and then this cropped up again so I'm not convinced on this yet. Fancy sensor works but the rest is still iffy. Will update this if I get it figured out or replaced.


New member
I just ordered mine last night, it pretty well covers all of the short falls of the older ones. I'll post back in a week and tell you what I think.


New member
Hydor smart level

Hydor smart level


Can you post a few word with your impressions of this unit ? Do you have any issues with waves in your tank and the SMART LEVEL sensor having a problem with waves ? Which pump did you decide to use with it ? I have a Tom's Aqua Lifter available to use if I buy the SMART LEVEL.


New member
I've been considering this unit as well. Things I'm not sure of in its design:

1. The female plug that you plug your top off pump to is NOT polarized (ie both slots are the SAME size), thus you have to pair it with a pump that has a non-polarized plug. The Aqualifter uses a polarized plug, so to use with the Hydor, you'll need to either grind down the wider plug blade, replace the pump's plug, or (least efficiently) modify the Hydor female plug. I understand that since the Aqualifter does not have a power switch, it does not matter safety or operational-wise that you're defeating the polarization. I'm NOT an electrician, so take this as it is. Others have posted success with modifying the Aqualifter plug.

2. I'm not sure why the designers chose to route the sensor wire out parallel to the alarm/high/low sensors -- you need to apply a cable clamp with adhesive to the glass to prevent the cable from rotating the sensors. It would seem to me that having the cable exit out the TOP of the sensor pad (ie 90 degrees up) would minimize the risk of rotating the sensor. See the attached micture.

If they made the magnetic mount using 2 magnets, it would also help hold the sensor level.

Otherwise, it looks like a terrific unit, especially for the price. I'm still considering it.

I also like the new CoralVue Smart ATO (http://www.coralvue.com/smart-ato-automatic-top-off-system-751) -- looks super slick, but I'd prefer to use the Aqualifter since my freshwater supply is farther away and I don't want to run extension cords or route that thicker hose to my smaller tank.

With the Aqualifter, I can run 25 feet of 1/4" tubing, which is much less obtrusive, and I can then use the Aqualifter (with mods) with the Hydor ATO.


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New member
Ok. I just got my Hydor ATO and it actually is quite terrific. The new ones DO support a polarized plug! My Aqualifter worked without modification.

I also now understand why the cable comes out from the sensor parallel to the sensor prongs. In a sump, it makes sense to come out the top since there is typically lots of space from the top of the tank to the desired water level, but on my 10 gal quarantine tank or any other tank where you want the water level right near the top, a cable exiting from the top will need to bend really sharply back over the top of the tank. On my setup, the ATO sensor magnet mount literally abuts the very top edge of the tank. If the cable exited from the top, it would make a very sharp bend over the top edge of the tank, and may tend to torque the sensor out. Not likely, but possible, and the wire gauge isn't so thick I'd be worried about strain, however I can now see the logic of the horizontal exit.

All in all, a great product. Happy with it so far.


New member
I have had the system for over 2 months now. I like it but there is a trick: you need to have the right pump or the alarm will go on quite often. The minimum running time is 10 seconds and the max is 1 minute so if your pump flow rate is too low, the running time will exceed 1 minute and trigger the alarm. If your pump is too powerful after 10 seconds the water level exceeds the max line then the alarm will be triggered as well...


Convince'em or confuse'em
Had mine about a year now, and no problems. I use a toms uplifter pump (as recommended), and occasionally soak the sensor in 50/50 vinegar and water.