I'm guessing on that sump in the picture, there would be a valve that opens at the bottom to drain the sump ever so often.

What I am thinking is that the bio-filter would do almost the same thing, being cleaned out every now and then. The water has cleared up pretty good since I have added it.

I was in a fish store yesterday and asked to see their sump, and WOW.. IT was a salt water sump, doing work ! But it looked too expensive for what I have. I'm more of the DIY guy. - ask the wife -