Black (I think) Algae that will not go away

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
If algae reappears, you can either try having a higher FC target or you can spot treat it (with black algae a Trichlor puck is sometimes used in the area).

As for the CSI, that's really more a matter of your SWG cell and the rate at which scale is formed. You could try for something closer to zero but until you get the borates in that may result in more scaling in the cell.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Ok thanks chemgeek that makes perfect sense... hopefully won't need to cross that bridge but I do have spare trichlor picks here if need & easy enough to alter FC target.

With the CSI, how negative could I go given my plaster situation? E.g. plugging in pH 7.5, TA 130 CH 300 (current results) and CYA 60 yields -0.17. Would this be ok to aim for? I can see the PoolMath mentions -0.6 and below problematic but just wondering for my own situation what a lower band should be (zethacat mentioned -0.3) to try and protect what's left of the surface (!).

Excited about moving forward with a sparking pool, here a pic from earlier today:



Thanks to everyone for the fantastic help & advice!!
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
Usually, -0.2 is sufficient to reduce calcium carbonate scaling in the SWG cell. Again, you'll just have to see what works best for your pool. Given your degradation, I'd to as high as you can before seeing too much scaling in the SWG cell. It's really up to you as it has to do with how frequently you need to clean the cell to remove the scale that isn't sloughed off from polarity reversal.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Usually, -0.2 is sufficient to reduce calcium carbonate scaling in the SWG cell. Again, you'll just have to see what works best for your pool. Given your degradation, I'd to as high as you can before seeing too much scaling in the SWG cell. It's really up to you as it has to do with how frequently you need to clean the cell to remove the scale that isn't sloughed off from polarity reversal.
Ok thanks chemgeek. Plugged in numbers into PoolMath and based on the higher CYA, and pH around 7.5 with CH and TA as is now it's about -0.17, but could get closer to zero if TA went up & pH would keep rising its not going to head more negative than -0.2 so thats good. Once I put in the borates in time I'll reassess it then but will also make a note of how often I'm having to clean the cell and go from there.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
Well you don't want TA higher because that will cause the pH to rise faster over time due to more carbon dioxide outgassing. TA is a SOURCE of rising pH. You'll want to lower your TA before you add the borates.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Thanks chemgeek I didn't know this at all! Had read random info that higher TA stopped pH rising but that's all totally disregarded now!

Will aim to lower TA to 80 as soon as I can, then aerate using jets to raise pH to 7.5.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Hi all, wish I was reporting better news but... whatever the black material/algae (if it is that) has returned in pretty much the same areas and new ones. It took a few days after stopping the SLAM but unfortunately it's back.

My test results are:

pH 7.5
FC 6
CC 0
CH 300
TA 140
CYA 45 (I stepped it up to 40 via PoolMath to see what FC level maintains before possibly taking it to 60 as per the Chlorine CYA chart).

I did an OCLT overnight and it comes out 0.5 loss (FC 6.5 midnight and 6 at 6am the morning).

There's no question the SLAM cleared up the water brilliantly, but part of the difficulty re whether the black material/algae was being killed was the pool cleaner sucks up whatever it passes each day, and I was brushing the pool daily also.

Is there any way I can better diagnose what the material is? Should I consider another SLAM with revised FC targets? (I held FC at 12 as per guidelines, my CYA was 25. The SLAM ran for some 9 days as well. I did mention seeing the black dust residue which happens when I brush the black material/algae away throughout.

I partly worry that perhaps this isn't algae. It doesn't appear to be mustard algae from what I read (especially since this appears in areas where there is direct sunlight). Could it in any way be residue from the gunite coming through? But it is seeking the same places and gets worse over time... like algae does..

Other question is, see the pics. In the first pic, see the little circles (much worse than appears in the pic)? This is how it's formed in some areas, as these little circles (single cell algae?) before getting more. In the second pic, it shows where the pool cleaner has run past and cleaned the edges but where the black material/algae is there where the cleaner doesn't often run past.


 

zethacat

LifeTime Supporter
What kind of trees do you have surrounding the pool? Is it possible some fungus is falling into the pool? I don't know, it's just a ridiculously wild guess since it makes no sense for this algae to be there if you are maintaining the proper level of chlorine in your pool.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Re: Black (I think?) Algae that will not go away - any help appreciated!

zethacat - I'm useless when it comes to trees, but do wonder... it def should be gone.

Jason, I haven't yet as I haven't actually been in for a while (weathers been all over the place here) and I needed to get a dropper or something to take the sample. I'll post back here as soon as I have & take a few pics when smeared onto paper.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Just a quick question, my FC is maintaining at 6.5 now, CYA 45. This is slightly above the target FC for a non SWG pool (but I DO have one). Should I raise CYA to 60 as per chart & lower SWG output till its around 4? Or keep CYA lower till I can sort this issue out as it's much easier to add it than remove it?
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Re: Black (I think?) Algae that will not go away - any help appreciated!

Hi, sorry for the double post. My FC is still maintaining about 6/6.5. Should I raise CYA to 80 as per the chart and then lower the SWG output slightly till its around 4 as per chart also?

The algae/whatever it is is still there, unfortunately the SLAM has not worked for me. Within 1/2 days it'll be back in the same spots again. It's probably a bit less than in those first pics, but if I didn't brush the pool every few days believe it would get as bad as that again. Ive tried to get down and take a sample but it's extremely difficult - it just blows away like dust almost.
 

Rocco

Well-known member
Dec 23, 2012
259
Manassas Park, VA
This may be a long shot but is it possible this is minor staining from copper or other metal? I had stains that would disappear and reappear that turned out to be copper staining due to the use of Copper algacide. I would add Calcium-Hypo shock directly to the pool and when it settled on the bottom the stains would reappear. After a while they would go away and come back again after I added more. However I do not recall having any dust/powder on the stains. But looking at the stains in the picture they remind me of the stains that I had.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
Very similar issue here just on a much smaller scale. My FC holds well and I don't have any green or mustard algae.

The black spots in the pic brush away like dust or get sucked up by the vacuum. Sometimes I think its dust that settles in crevices in the plaster and sometimes i think its black algae.

Any help would be greatly appreciated.

View attachment 34179
So interesting someone else is having a similar issue... It sounds very similar. If you leave it for a few days and don't let the cleaner suck it up, what happens does it get larger?

I got the pool testing kit, have kept levels perfect almost religiously, did a SLAM but all to no avail, the issue is still there. The only definite thing I notice is the algae/dust/whatever it is seems to come up more where there's pitting in the plaster surface.

I've tried sitting triclor pucks on areas to spot treat, but it has no effect. I can't even take a sample (as a few people suggested) because it just gets pushed away like dust. Yet leaving it untouched for days definitely makes the spots worse and form larger, just like algae.

I'm at a loss as to what to do.

Rocco - mine isn't copper stains, I actually used copper algaecide last year as one way to hopefully eliminate the algae/dust stuff, but to no avail.
 

Nitedr

Member
Aug 28, 2014
17
West Covina, CA
So interesting someone else is having a similar issue... It sounds very similar. If you leave it for a few days and don't let the cleaner suck it up, what happens does it get larger?

I got the pool testing kit, have kept levels perfect almost religiously, did a SLAM but all to no avail, the issue is still there. The only definite thing I notice is the algae/dust/whatever it is seems to come up more where there's pitting in the plaster surface.

I've tried sitting triclor pucks on areas to spot treat, but it has no effect. I can't even take a sample (as a few people suggested) because it just gets pushed away like dust. Yet leaving it untouched for days definitely makes the spots worse and form larger, just like algae.

I'm at a loss as to what to do.

Rocco - mine isn't copper stains, I actually used copper algaecide last year as one way to hopefully eliminate the algae/dust stuff, but to no avail.
My question got moved to another thread and I was told it is more than likely just dust. I believe it. I have a lot plants in the backyard and a huge pepper tree right behind my pool that is really messy so it makes sense.

My plaster is fairly new (previous homeowners re-plastered a few years ago) but whoever did it did a terrible job and it does have some mottling and is not completely smooth. Other parts of my pool also get a lot of dust on the floor not the walls like in the picture. I think the dust doesn't stick to walls except for the crevices. This part of my pool in the picture is my deep end and the circulation in this area isn't great because the jets point towards the far end of pool.

You may just have a dusty pool. Mine has the same dust in the same area within a couple of days of vacuuming. I just put my aquabot in there more often now to help with the dust. My paranoia just had me thinking it was Black Algae.

Sorry, drewh. Wish I had more for you.