It sounds like it was just muddy water from the deluge. The fluff is soil that has settled, and fish will dust everything off soon enough. The soils that were brought in with the runoff will probably not be an issue.

You can do a "jar test" by getting a sample in a glass jar and just letting it sit undisturbed for a few days to verify it all settles out...keeping a second jar sample in a dark closet will let you know if it is algae...(the sample in the light will not clear, but the one in the dark will, if algea)