Yellow/Brown dusty deposits that reappear repeatedly

[matt4x4]

Wayne, this stuff we're talking about is DEFINITELY a type of Algae, it starts like deposits in spots, if left unattended, it gets to be more and more, what you don't really notice (until you start to vacuum) is that the whole floor will get a thin layer on it - it's so even that you think your remaining liner is spotless, however, turn the vac on and see the color difference. The walls also get it - more on the walls with shade and relatively hard to see.

[matt4x4]

That's it, when your pool water starts to look that aqua blue/green milky look, you're finally killing it off, another 3 days of filtering with the DE and you should be clean.
PIAlgae is what it SHOULD be called!

[chem geek]

I've had my cl levels at about 30 for 3 days now. pump on 24 hours/day.

Pool is definately clearing up.

An FC of 30 with a CYA of 40 (that you mentioned in an earlier post) is a disinfecting chlorine (HOCl) level of around 1.3 ppm (an FC of 25 is an HOCl level of around 0.8 ppm) so it looks like we are narrowing down the amount of chlorine needed to kill this stuff to be a minimum of at least the column of 1 ppm in this table. If others have this problem with different levels of CYA (especially higher), then we can confirm this and eventually update Ben's Best Guess CYA chart to have at least two shock columns -- one for plain green algae (probably a 0.3 ppm level) and another for this mustard/yellow algae (probably a 1 ppm level). That leaves black algae where others have written about rubbing Tri-Chlor pucks on the algae, but I'm not sure about what overall pool chlorine levels are used at the same time to be effective.

Thank you all for keeping track of your chlorine (FC) and CYA levels during your battles with this algae. I know that the chemistry of what's going on is the last thing to enter your minds, but this information will ultimately help others.

Richard

[Wayne LaBanca]

OK, looks like were getting some good analysis going here. I'm not arguing that is not algae, I just think it's stil questionable. Maybe what I had/have is not the same thing. Does anyone know of a type of algae that just settles rather than attach? This is very interesting, maybe we are on to ta new strain???

Wayne

[jimmyzshack]

I have this same thing, started about 3 weeks ago. i thought at first it was from the dog getting into the pool. just put 3 big walmart ultra bottles in pool is about 12k gal. and have 3 more in the car. I vac the bottom sun and it was back tue. so i will keep the fc up about 20 for a few days and vac again sun and backwash.

[fuelman]

Hello everyone!
I've been tring to find out what this stuff is myself! I had to drain and refill my pool about 2 weeks ago so the installers could add some more sand under my liner due to settling. I drained it down to about 2" then it rained the next day.
We got 3" of rain which sat in the pool for another day till the installers came to do the repair. Anyway, I started refilling the pool after they finished.
Once full I added 4lbs. of CYA, and 2GALS of pool store chlorine approx 6%.
I checked the CL. level the next day and it was 1.0 PPM so I added more to bring the level to 4 PPM which is where I wanted it. It held there for about 1 week then this stuff showed up. First I hand vacuumed and it came back a little at first then it got worse till it covered most of the bottom and I've been adding about 1/2 GAL of chlorine daily to keep the level at 3 PPM. Then I PANICKED. I went to the pool store ( Pinch-A-Penny) and let them sell me some Super Green Algicide. I dosed the pool with 4oz. as per directions.
and let it work for 24 hrs. then vacuum to waste buy hand. Looked real good just a little cloudy. This was yesterday, This morning I added 3/4 GAL of chlorine and went to work. I just got home and checked and I think it's back just a very little on the bottom so I have the auto-cleaner running now.
My numbers are CL 3.0
FREE CL 4.0
PH 7.4
CYA 40
COM CL 0.0
TO ALK 125
My pool is a 10,000 GAL Above Ground w/ a Clearwater 2600 sand filter What can I do? Help.

[mbar]

I think what you have put in your pool "super green" algaecide is an aglaecide that has copper in it. This being said, you may have a problem when you raise your chlorine to shock levels, as you may get some staining due to the copper in the algaecide which I read is 7%. Hopefully the algaecide has a sequesterer in it that keeps the copper in suspension. It really is not a good idea to introduce any metals in the water. High chlorine levels will kill any algae, you just have to keep it high enough long enough for it to do the job. With a cya of 40 you need to take your chlorine levels up to 15ppms and keep it there being very consistant. Everytime it falls below 15ppms, you have to add enough chlorine to take it back to 15. If you read through this thread, you will see this algae sometimes needs even higher levels of chlorine to kill it. I would suggest that you take your chlorine up to 15 - 20ppms and keep there, brushing and backwashing as needed. Be very consistant!!! You may want to drop your ph down to 7.2 while you are shocking the pool to help keep staining away. If you are consistant with the high chlorine levels, and keep your filter running 24/7, you should be able to get rid of this once and for all

[chem geek]

I've been doing some thinking and looking at the numbers for this hard-to-kill yellow/mustard algae. Though it appeared that high chlorine levels were needed to kill this algae, my saying that it was around 1.0 ppm disinfecting chlorine (HOCl) assumed that the pH was around 7.5. Normally, the CYA acts as a chlorine buffer so higher pH doesn't change this concentration by that much, but this buffering starts to fall apart at the higher HOCl concentrations needed to kill this algae. What this means is that perhaps the actual disinfecting chlorine concentration needed to kill yellow/mustard algae is not 1.0 but is less, perhaps 0.7, but adding a lot of chlorine makes the pH rise which results in less disinfecting chlorine than I was assuming.

For practical purposes, using this chart when you start at around a pH of 7.5 and then add chlorine it is probably OK if you use the 0.3 ppm column (or at least 0.2) for green algae and the 1.0 column for yellow/mustard algae. However, next time this happens to someone, we should try to not only add chlorine to raise FC, but also start out at a lower pH (perhaps 7.2 or even 7.0) or add acid to keep the pH lower since that will allow for lower FC levels to kill the algae (meaning less bottles of chlorine and therefore lower cost).

I suppose this will have to wait until next August to see... Of course, everyone will probably be adding PolyQuat 60 and/or have 50 ppm borates in their pool and no one will get yellow/mustard algae so we can "experiment".

Richard