hydroponic sub pump question

I got a hydrokit similar to stealth hydro kit whit the tubes on the net pots and all can some one tell me if i run the sub pump always or specific time to it [Thanks to the helper] here is a link of the similar kit the six pot Thanks again http://www.stealthhydroponics.com/index.php?a=SHH9&gclid=CNSIsveqmqYCFUdN4AodiAedoQ

Run it all the time Or not at all ..Or just as the roots drop and then shut it off after they hit the water..Any of these options are acceptable