Here are some more beginner's questions: I'll be lining my grow bed in my first ever AP system with pond liner. Do you have any recommendations on the thickness of pond liner? Any tips on how to make good, tight outflows through the liner? I'll try to build a bell siphon like this one: http://www.youtube.com/watch?v=oDzcKgWLRf0&feature=related Any tips or warnings? Thank you! Louise