Surface agitation is bascially the amount surface current that is being generated by your filtration method. If your spray bar or output is near the top of the tank, it will obviously disturb the surface. CO2 is a lot easier to get rid off than it is to put in. Vigorous surface currents will "outgas" your co2from the tank, and quite effectively if I do say so. Make sure your filter ouput is directed away from the surface; some agititation is ok but I would minimize it as much as possible.
Like argblarg said, I would test your pH in the morning or after you Co2 has been running for about 3 hours. If still no different start questioning your test kit. A good CO2 drop check, pH, and kH test will give you peace of mind because you can cross reference your results.