Is this dirt/pollen or is it algae?


New member
May 30, 2019
Nashville, TN
Just in the last few days we've been having problems with what appears at first to be dirt in the bottom of the pool, but I'm wondering if it's an algae bloom. It's very very fine greenish brown particulate matter, and as of this morning it seems to almost cover the bottom of the pool (which is small - 36"x15' summer waves), but the water was very clear until I started trying to vacuum.

First, we got lazy about testing and our chemistry got out of whack which turned the water slightly cloudy Friday afternoon. I noticed it before we saw the stuff at the bottom of the pool and then Saturday we started seeing the areas of "dirt" settled in the bottom. I think the cloudiness could have been a separate issue, because we raised the ph and chlorine levels to normal and the water appeared to clear up. I also filled a clear glass with pool water this morning and to the eye in the sunlight the water itself looks perfectly clear. However we still had areas of "dirt" on the floor of the pool. I try to vacuum and I guess some of it does come up but 90% of it seems to disburse immediately when it's disturbed by the vacuum, which then turns the pool cloudy again, but more of a greenish cloud rather than the first day we noticed any problems, when the cloudiness appeared to be colorless. The greenish cloudiness remains until the particles settle and we're back to clear water but dirty floor.

I'm inclined to say dirt based on 2 things: I tried to get some on my finger by sweeping my finger on the floor where it is, and nothing sticks to my finger at all. It's not even the slightest bit greasy or tacky, it just floats away. The second clue is that it is only on the floor of the pool. There's nothing at all on the sides, and I assumed algae could grow pretty much anywhere that's below the waterline.

We definitely need to upgrade our vacuum so that we can actually pick it up rather than just push it around, whatever it is. But if this sounds like it could be some type of algae based on my description that would be very useful info in terms of what to do going forward to stop it growing.

The pool is under trees and there has been much more debris falling in lately in general. The leaves in most of our trees start to turn yellowish then brown in late summer and they drop lots of leaves early, and this had started happening right before the problem began. We've also been having crazy heavy rainstorms which have been blowing debris into the pool and also probably contributed to the chlorine and ph dropping.
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