I agree. My Aqualifter struggled to lift the water. It would pump about 2' up, and 2' over, and after about three days of that you can tell the diaphragm was getting beat because the flow slowed to a drip or two per second. My ATO needed to be active for over 30 minutes to top off 150ml or so. That wasn't going to work for me.
I installed a shelf system next to my tank, and housed my reservoir and AquaLifter to be about level with the tank itself. So now, it's a steady stream of water which is pumped about 30" or so horizontally, and the pump isn't being over worked. Only stays on approximately 50 seconds and dumps in about 150ml, 4 times a day.