Not sure about these spots?

[alanrmeadows]

Can anyone venture a guess as to what these spots may be? I realize the clarity of the picture isn't great, but it was the best that I could do today. They are darkish-brown in color and will not brush up with a regular pool brush. They are both in the shallow end and deep end of the pool. My guess is that they are more prominent in the "blistered" areas of my fiberglass pool. Below is my photobucket link.

http://i1016.photobucket.com/albums/af2 ... ots001.jpg

Thanks,
Alan
17,500 Gallons
Fiberglass
Inground
Sand Filter
South Arkansas

 

[JasonLion]

It is difficult to be sure from that picture, but those look like organic stains to me. Organic stains will fade slowly over time, more quickly if you raise the FC level. You can double check by holding a trichlor tablet against one of the stains for a minute. If the stains fades, chlorine should take care of it.

 

[alanrmeadows]

But most likely not some sort of algae?

Thanks,
Alan

 

[alanrmeadows]

I should also point out that I've had the FC very high (at shock level or above) for about 2 weeks and have noticed no change in the color or intensity of the spots.

Thanks,
Alan

 

[JasonLion]

Algae will brush off, though sometimes it will just come back. If they don't brush off they aren't algae. Algae can leave organic stains behind that don't brush off, but there is no live algae in those stains.

Try holding a vitamin C tablet against one of them for 30 seconds and see if that does anything.
If that doesn't do anything, try the trichlor tablet.

 

[alanrmeadows]

I'm sure this is a stupid question...BUT, we're not swimming yet so what is the best way to actually place and hold a vitamin C tablet on those stains? I'm sure there are creative ways to do it, I just can't think on any right now.

Thanks,
Alan

 

[JasonLion]

I'd put a couple of vitamin C tablets in a sock, tie the sock to a pole, and hold it in place with the pole.