You always need an airstone or other aerating device for standing water. Plus if you are going to deliver water to your roots, it is beneficial to have a decent amount of dissolved oxygen in it. as toastycookies stated, you probably don't want the water pump on 24/7. Put it on a timer and let the roots get some air. Although some people here do run it 24/7, but they also maintain a high amount of dissolved oxygen in their water stream.
Cheers!
Mr. Bond