Okay, I just finished building my 315G with dual sumps under the tank. I started off using filter socks, 2 on each side and ended up removing them. They clogged way too fast for my taste. If you are building, incorporate overflow boxes into your build and use that area as a mechanical prefilter. It's a lot easier to clean filter boxes then it is to crawl under the tank to clean out filter socks. I built my own sump and ended up tearing it out and replacing it with 2-50G totes that contain poret foam and assorted filtering pads. Water is crystal clear and maintenance is simple. You can see what I ended up with in the thread below. Go toward the end for my newest sump.