Filter portion...correct, u need a powerful pump. But according to some keepers, the recommend that the pump do not suck up all the poop but more of water. Poop must be removed manually everyday and not by the pump.
Confusing right ?

So if u r using an eheim, u shud put the inlet at the mid level of the tank and not at the bottom. Then watever poop there is will be collected at a certain point depending on the flow of ur tank current...

Plecos will poop a lot...so that means that you will be very busy. But as long as there is wood in the tank, they will never go hungry...