Since you have a AC already, Id get a small pump and dose kalk.
Aqualifters are suppose to work pretty good, otherwise theres a perilistatic one that DonW recomends that wont back siphon(the sp3000 will require cleaning the check valve on a bi-monthly to monthly basis).
With the AC you can use the OSC function to run it. This way its added slow enough to not cause any sort of dangerous PH rise, and wont percip out. For my 38gal tank I dose kalk at night only to keep my night time ph up, but since you want your PH up at all times, you can just run it continuously. The code would look like "OSC 001/XXX ON/OFF Then DOS ON". XXX would depend on a lot of things including the rate at which your pump moves water, your evaporation rate, and calcium/alk demand. Too give you some sort of ball park, I run mine 14 hours a day(main lights off) at 001/014 and that seems to only require some supplementation for my tank.
That alone might not give you the ph boost your looking for, but in the end if your calcium/mag/alk/oxygen levels are all where they are supposed to be, I wouldnt worry about the lower PH to much. That seems to be the consensus of what I have read on the board.
Peace
