What is this?

[sunofthebeach]

I have this blackness that has spread on my grout to my plaster and on my coping piece. I dont know what it is , where it came from or how to get rid of it. It is only in that 1 foot section of the pool.

the pictures did not come out so good.

1st picture top view of the tile
2nd pic front view of the tile and coping
3rd pic view of the tile you can see where the black is spreading to the plaster

Anyone know what this is ?
How to get rid of it?
Is that black alge?

[sunofthebeach]

the rest of my tile looks like this

[Simmons99]

stupid question - but have you tried pouring a 50/50 water bleach solution on it and letting it set? It could be like mildew - does it stay wet there all the time (like from a mister or water feature)? I get something like that on my concrete walk-ways where there is moisture and little direct sun.

[sunofthebeach]

stupid question - but have you tried pouring a 50/50 water bleach solution on it and letting it set? It could be like mildew - does it stay wet there all the time (like from a mister or water feature)? I get something like that on my concrete walk-ways where there is moisture and little direct sun.

I tried to power wash it no change, and I have poured bleach on it, but i did not really scrub it. There was no change. It does not stay wet.

[sunofthebeach]

I have noticed a couple other spots that are developing around my pool.

Can anyone say it is not black alge?

[sunofthebeach]

My pool builder was out today. The black staing on my coping is Iron Ore that was in the flagstone when it was harversted. It leaches out over time.

they are going to replace it for free as it is defective material.