water from your 150 goes into an overflow (look up eshopps and cpr if you need an external overflow) that water goes through piping of some sort (hard or flexible pvc is used most often) The water then goes into your sump /wet dry. usually this is where your mechanical filtration is usually a filter sock on where the pipes drain into the sump the water will then travel to a baffle (divider) to your biological filtration (your choice of bio media here I use a drip tray to pot scrubbers) also in this section feel free to use heaters, extra air stones etc... the water will then go into another baffle/divider where you can have your pump. your pump then has pipes (hard or flexible pvc is used most often) that bring the water back up to the tank.
The stickies in the diy filter section really explain everything in great detail, how to size an overflow how to size a pump etc....
