Normal sump pumps are not designed for continuous use, you need a pond type pump such as a Laguna or Mag Drive, there are many suitable brands available. With a 135gal tank and a 20 gal sump, you should have a 5 X per hour turnover rate, so you need at least a 750-900 gph pump, depending on what kind of fish.
I have riverine cichlids, so my smallest pump is a 1200gph Mag Drive in a 20 gal sump,
on my 300 gal bank of tanks I use a Laguna 2400gph model in a 55 gal sump.
I have a 55 with with a aqueon 75 quietflow filter on it now and want to add another filter. And to compare filters I was just comparing on matching gph