nft type of gardening

[DAMAN]

RON!! I'm using the nft type of gardening in a homemade planter. its a 12"/12"/12" box with a 3' piece of 3"i.d. pvc run through. I run a 15 gph pump into both ends of the pvc constantly and the nutrient solution drains into the center. my questions are 1 when I turn my pump off all the water drains back into the tank.(syphon) do you know of any easy backflow controls? Can I run my pump only 15 min every hour? I also have a 8" bubble wand (no Im not bragging) directly in the pvc. will this give the roots enough o2 and keep the water from stagnating? Im currently growing sweet peppers and 2 birdhouse gourd plants I transplanted about a week ago and the peppers look great but the some of the leafs on the gourd plant are kind of wilting on the sides any ideas, comments? Im using hydro farms liquid all purpose 7-7-7 THANKS RON U DA MAN!!!!!!!!!!