Ph for Aeroponics or any hydroponics is 5.2 - 5.5 but in truth you can go up to 5.8 - 6.2 and still be ok later in the cycle. (Like after the first 30 day's)

It will creap up but you should bring it back down every day sometime twice a day. to normal range. 7.0 is more for dirt farming and not Hysroponics