Do I have Mustard Algae?

[George D]

A pool pro told me that I have mustard algae at the bottom of the pool and I need to shock. It looks like dirt and the lighter color dirt looks like sand from the filter. I don't see how because my test kit consistently scores at 0 or .5CC. I attached photos. He also thought that the visible stains in the first pic was mustard algae also.
I also noticed what looks like tiny snails underneath the dark dirt during vacuuming. Is this normal? He also stated that it's better to use granular chlorine, especially for shocking.

A question unrelated to this issue is, if I will not be opening the pool next year, is it still necessary to shock or add polyquat 60 algaecide during the closing?

 

[jblizzle]

Of course is not normal to have things growing in your pool

I think you may have a misconception that algae can only start if you have cc's. That is just not true. Algae starts due to lack of chlorine. CCs are the temporary byproduct of the chlorine breaking something down, but it is not uncommon to have algae and not have any register in the test.

You need to fully the SLAM Process process. And then perhaps review the mustard algae article in pool school.

Even if you added those products when you closed and your water was clear in the spring when you would normally open, there is no way the pool would not go to a swamp being neglected all summer. So not likely much point.

 

[George D]

Ok, Thanks for your quick reply. I also thought that since the pool was sparkling clear that it could not be algae. Should I stick with liquid chlorine or is granular ok during the SLAM?

 

[jblizzle]

Depends on your test results and whether your pool can handle the side effects

 

[George D]

Ok, to confirm, both pics I posted above are of mustard algae? The reason why I ask is I read in another post that mustard algae is not black. Also the green color at bottom of the pool in the first pic, with the black dirt are stains not algae.

 

[jblizzle]

Doubtful it is mustard algae which seems to be fairly rare.

 

[George D]

Sorry for all the questions but is the pic with the black dirt black algae instead?

 

[jblizzle]

No way to tell from the picture

 

[George D]

I took 2 more pics. I picked this up what I thought was dirt, from the bottom of the pool.
Is this algae and if it is, what kind is it?
If this is algae, it is not consuming the chlorine and it does not register as CC. If I understood correctly, it was explained earlier that you can have some algae in the pool and still have a CC of 0 or .5.

 

[mknauss]

Smear it on a paper towel. Does it have a green hue?

 

[George D]

I will have to try that tomorrow and get back to you. Thanks.

 

[George D]

Yes, I smeared it and it turned green.
What type of algae is this?

 

[jblizzle]

Is it stuck to the pool in distinct spots? likely black algae, but I have never been able to get a chunk that big.

 

[JamesW]

Looks like black algae, which is actually a type of cyanobacteria. It looks like you also have other algae as well. Maybe mustard.

Cyan means blue-green. Black algae is not black or algae.

 

[George D]

Yes, in the bottom corners of the deep part and over the lines at the bottom of the liner. When I tried to scoop some up with the skimmer, most of it was dissolving. All these black spots are at the bottom of the pool. There isn't any around the walls. Does this mean anything?

I read the Black Algae-Pool School. It states that it's almost impossible for black algae to grow in a vinyl liner pool. It also stated it could be a false alarm, where it might be granular fertilizer.
Should I start the SLAM anyway? Should I brush first before I start the SLAM.

 

[George D]

Test kit results.
FC-2.5
CC-.5
CYA- less than 30. Black dot clearly visible.
I did not shake sample vigorously as advised by Chem Geek in one of his comments. Took CYA test a 2nd time, same results.
Should I shock at mustard level? With a CYA of 20, that would mean FC of 12.7.

As of 6:30PM
FC-15
CC-0.

 

[George D]

As of 11:30AM
FC'-9.5
CC-0. I added 2 gallons of 12.5% liquid chlorine which should bring FC to 16.5.
As of 1:45PM. FC-13.
In between the tests, I vacuumed some algae and pasted this pic. Is this an egg? What type of algae is this?

 

[TeanyV]

That looks like a roly-poly bug. I find a lot of those, especially after a storm.

 

[George D]

Ok, Thanks. I'm continuing with the SLAM.
Test results as of 2AM. FC-10, CC-0. I added 1 gallon of 12.5% chlorine to raise the CL level between 13-13.5.
I see some of the black spots again at the bottom of the pool.
Is it possible, as I brush and vacuum that the small algae particles go through the filter and back into the pool from the returns? How often should I Backwash? The pool is crystal clear.

 

[George D]

After vacuuming and brushing it's still coming back at shock levels.