Okay, I should just go buy one and look at it, but just wanted to do some background research on it. I want to use it to dose dechlorinator into an aquarium and wanted to think if this will work. Yes, they sell VERY expensive ones for this purpose, but why spend more when you don't have to? http://www.amazon.com/Gilmour-Soluble-Fertilizer-Feeder-405/dp/B000XTK92W Anyway, is this like a venturi pump? I'm guessing the pressure from the flowing water creates a suction? I'm an electrical engineer, so I have basic physics background (for the purposes of knowing how much to dumb it down for me :P ) Thanks in advance!