one pump is enough for a 180 gallon but 2 is fine. I will go with 2inch pvc
or 1 1/2 inch pvc
. as for the spraybar u can run it in the back of the tank(inside)lol, with holes ... so the spraybar will be as long as the tank.
if u like u can run the spraybar like a air bubble. set it on top of ur sand and let the water spray up like a air bubble tube.
i dont run strainer on my overflow, and it suck sometime when feeding them pellet, y? cuz it will just be drains down the pipe.
like my duckweed, it just keep getting drain down.