A: The "overflow pipe" runs back to the tank and does nothing more than run extra H20 back to the holding tank; this is done so your system does not "OVERFLOW" causing waist.
A: For the 11 plant system a fish tank power head which pumps H20 +/- 140-260 GPH (gallons per hour). If you us a bigger
pump just divert the H20. In fact, if you search this web page you will find a pic of it.
A: the "1/2 inch threaded inlet" is how the H20 solution is pumped to your system. You connect the 1/2 hose upto your pump and then to the 1/2 inlet.