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.