Is this black algae?

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adeller

adeller

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Sep 2, 2011
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I have a question about some staining issues I am currently having. Here are the most recent test results:

FC 3.5 (bumped it up to 4 last night)
CC <0.5
pH 7.5
T/A 80 (brought pH down last night and aerated)
CH 310
CYA 50 (low, I know, added some CYA again. It seems to keep decreasing)

The last OCLT test about two weeks ago was OK.

These two pictures are not great, but has been a little breezy the last several days.

http://i1131.photobucket.com/albums/m555/artdeller/107.jpg
http://i1131.photobucket.com/albums/m555/artdeller/106.jpg

How it started was with one or two spots at the corner of the wall and floor about1" in daimeter, irregular in shape and grey in color. Now there are more appearing as small round dots, dark in color. The chlorine tablet test was inconclusive. However, the increase in number is leading me to believe that this is some kind of black algae. (Of course it is the first week after school ended and the wife doesn't want me to shock the pool just yet, ugh.) My plan is to run the OCLT test tonight and begin shocking after that. Does this sound like an appropriate plan. From reading posts on this I assume I need to rub these spots down with a pumice stone and then shock. Which shock level am I looking for? Pool calc says 16 for normal shock and 29 for mustard algae.
 
That doesn't really look like black algae, though sometimes it is difficult to tell. Before shocking, feel a spot and see what it feels like. Black algae will be slimy and you will be able to scrape a little off with your fingernail.
 
OK, I didn't think they felt slimy. It started with 1 or 2 and now there are about 6 or so spots. They don't brush off with either the pool brush, wire brush or pumice stone. Is there another test to try?

While I am at it, there is another issue I am having, but I don't think it is related. A few of the returns have a tan colored stain below them in a fan shape, where the return was exiting. these returns exit through a slit, so push a fan shaped plume of water, directed down. It is more prominent in daylight and does not respond to the pumice stone, at least not that I can see. The below picture does not do it justice. I am thinking scale, but how do I get rid of it?

108.jpg
 
JasonLion,

Thanks for the really quick responses, and the great resource this site is.

Iron stains? OK I'll try it. Where would the iron come from, the fill water? If they are iron stains, how do I get rid of those?
 
adeller said:
JasonLion,

Thanks for the really quick responses, and the great resource this site is.

Iron stains? OK I'll try it. Where would the iron come from, the fill water? If they are iron stains, how do I get rid of those?
Click to expand...
If you only have a few small spots, you can crush cheap vitamin C tablets in a sock and hold it on the stain for a few minutes.
 
Bingo! :-D Vitamin C did the trick. Thank you again. I didn't think it could possibly be iron. SO the question is, would that be iron from the fill water? If so, what did I do to make it precipitate?
 
Probably not from the fill water since it was just in a couple spots. More likely it was from something that fell in, like a Bobby pin, some ironite fertilizer, of some pieces of metal from you nextdoor neighbor's angle grinder.
 
A tiny piece of steel can leave a sizeable rust stain. It's amazing, really. After we had a new fence put up, there was the expected dirt, but also tiny pieces of metal - probably broken off nail heads or something. BIG rust spots. A nylon full of Vitamin C and a smooth rock for weight, all tied to a long string, got rid of it.
 

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