What is this?

[MMM33732]

Its recently been growing in my sump and fuge. Never saw it before. Its white and looks like a Spiders nest. It feels very slimey like its mucus. Theres no live animals in the sump that could be making it. In the fuge, there the same thing starting to cover all of th sand along with long strands of cyano, but it looks more yellow in the fuge. Any ideas? The first two pictures are of it in the sump around my skimmer. That chunk of it is about 5x5. The last picture is of the fuge, but its pretty hard to see it on the sand bed.