ATO Problems, What Pump To Use?

I am new to saltwater and I just purchased a JBJ ATO Unit, I have the Aqua Lifter Pump. I have it hooked up to my 75 gal tank. I am guessing that my Lifter Pump is not big enough to push the water up my head space. I have the pump under my aquarium and one line into a 5 gallon bucket and then the other runs up the back of the tank. So there is probably a 3-4 ft that the water has to travel up to the top of the aquarium. If I bring the hose down closer to the bucket instead of at the top of the tank it will work. As soon as I move my line up to the top of the aquarium to run into it, all of the water stops. I was wondering if anyone else has it set-up like this and if so what pump are you using or if there is a better way of setting it up to work? Please help me, this is driving me nuts, lol!!! Anyway, any suggestion would be appreciated. Thanks Rich