I am just going to throw my 2-cents in here since I run a very high aeration rate myself that is super high... I use Cultured Solutions nutrients who point out that when you pass a certain point in aeration they recommend that you cut the nutrients by 1/2 their recommended rates. What that did for me when I tried that was I saw my plants really rocket off and the root balls explode in size far bigger than anything previously noted. I too used to have a serious pH drift to the higher end, and yet it didn't make any sense because my reservoir was huge for only a couple plants and still I saw the pH drifting higher and higher by the hour... Turned out I had to switch the brand of pH Down I was using, because before I was using the common 35% phosphoric acid (standard pH Down) and instead had to switch to the Pharmaceutical grade pH down which uses 1/10th of what I used to, but it did finally stabilize the pH issue for me. My issue with pH is from my water supply, which could be where your problem is as well... what is the pH and PPM's of your water supply?
