I initially thought that it was coming from the sump because I had a good 1/2" of detritus build-up - but last week or so I removed my sump, took out all the rock - and cleaned the sump out. The next water change the same thing happened.
My pump is in the sump.
I just wanted to make sure all of the stuff getting kicked out wasn't going to add a bunch of nitrates or other undesirables... It settles out pretty quickly, within 30-45 minutes, I can't even notice.
As I said, I just wanted to ensure it wasn't detrimental to the water quality.
I also didn't have a filter for the same reason - lots of pods