Help,not sure what this is on bottom of pool

[CallMeIshmael]

It sure sounds like yellow algae.

Ahhh, ignorance was bliss... It appears we have a similar thing happening in our pool as well this year. It's the first time I've noticed the brownish "mud" on the pool floor and it matches the descriptions here.
I've also noticed that the shade-side wall of our pool (fiberglass) is slightly more yellow than the sun side in an area that was bypassed by the return flow.
Lessons learned: I'll be adopting Matt's 3rd year approach to killing off whatever this stuff is, and hope the shock will also clear out what may be "yellow algae sheets" (ewww!) on the shade wall. I'll also be adding a return eyeball to direct flow (and chlorine or other treatments) towards that wall.

Thanks for a helpful thread & I hope the heavy shock/brush routine works out!

[itstoohot]

I think you are dealing with mustard algae. I had a wake up call with this stuff in June. We noticed it towards the end of last year and thought nothing of it until it consumed our pool this year. Our daily regimen was to increase the chlorine to shock level (we intentionally overshot this regularly) in the morning and evening, vacuum, change cartridges (we have a cartridge filter and an extra set of cartridges) and run the filter 24/7. We also used skimmer socks to grab what they could. At the worst, it took nearly 2 weeks to be rid of it. Now, we seem to get it whenever we use the solar cover or if I haven't brushed the pool in a while. If caught early, we just shock, brush and let the filter take care of it and it's typically gone the next day.

My fight - http://www.poolforum.com/pf2/showthread.php?t=3287

[haze_1956]

I have been getting the same thing for a few weeks. (the stuff in the OP's photo )

Had this stuff sitting at the bottom for about 5 days, a bit more appearing each day. Has a nice brownish green color and sort of smears a little when you vacuum it.

It seems to be pollen and dust collecting in the little divots in the pool floor. It only appears on the floor, never see any on the walls. We've had no rain to wash the pollen and dust into the gound, so I think it is blowing around and settling in the pool.

While it was there I didn't have an increase in Cl demand or any CC reading. This is another reason I tend to think it wasn't algae.