For the past several weeks we have what appears to be yellow dirt and some black flecks on the bottom of the pool. We have a DE filter and the pool is about 9000 gallons. At first we thought it had somethin to do with the pucks, because it would be fine after vacuming and within a half hour it was on the bottom again, but it also happens if the filter isn;t running. It is very fine, it you hit it with the brush it goes up in a cloud. Could this be mustard algae. The black particles are very small and almost look like gnats or something.

Thanks