Just starting out with a few questions about this DWC system as the directions were not clear. #1 - Does the air pump stay on 24/7?. #2 - Does the water level have to be touching the bottom of the pebbles or is there some space between the two? I'm asking because I think I am overwatering as the bottoms leaves have shriveled and fallen off the plant and in general the plant doesn't look too healthy and not growing all that well. Any suggestions would be greatly appreciated. Thanks.