wilma4, pebbles, 400w hps slow growth

hey ppl, my plants are growing at a slow rate and i have to be honest:
first of all i don't know how to schedule the water pump, right now it's at 15 mins per 3 hours.
the other problem i have is the ph and the water from my city seems to be 7.5, what can i do? ph can make my plants grow slow? thank you!

[video]http://img830.imageshack.us/img830/2783/imag0120l.jpg[/video]

you can run the pumps for as long as the lights are on if its a drip system and buy PH down so adjust your ph level

nutrients arent plant available if the pH isn't in the correct range.
That being said, I spend my first year of growing hydro without a pH meter.
Luckily foxfarm nutes are pH stable.

If you have the flood drippers - on for 15mins every 2 hours while lights are on. As they grow you can switch to 15mins every hour when lights are on.

If you are using the drip drippers - my understanding is that they stay on all the time while lights are on, but don't quote me on that one as I use the flood drippers.

Thats a strange looking wilma system. Does it not use the pots that sit on the tray?