Is that stuff all over the outside of the overflow box what we are talking about here?
Your sock just looks like a dirty sock and I'm really not seeing anything there to be concerned about..Certainly not to keep restarting a tank over..
If its the overflow scrap some off throw it on a paper towel and snap a pic..
Right after that just scrape it out/siphon.. It looks dirty man.. fix that
Oh and woot woot to Crystal Lake.. I'm a LZ native stuck down with all these rednecks