Whats this?

[Winstonselect848]

Pool( 16x48, 5100gallon) has been not used and covered with solar cover for about a week. I use a sand filter(intex 2800gph). Today when I went to take water sample( test daily, BBB, Taylor 2006) I saw patches of what at first I thought was dirt. When I went to brush it immediately disappears. Even with just light waves from the brush and pole it is easy stirred up. Looks light brown or maybe green. Then I quickly noticed it covered the whole bottom of the pool is covered with a light coating. I got in the pool to see if its slimy. It is not slimy. But me walking around stirs it up very easily and makes pool cloudy.
Is this mustard algae bloom? I test and add chlorine everyday. FC is almost always kept at 3 or above. CC is either 0.5 or 0 Here's some pics( not very good). And early evening last nights test results.Dirt, Algae or maybe pollen?
After reviewing some post in the forum I chose to do an OCLT, Over Night Loss Test. I tested @ 6ppm FC last night at 830pm and 6 ppm this morning at 6am. CC is always .5 or 0. Now I'm really not sure what this is. Should I SLAM just to be on the safe side? Here are a couple pics. The clean area s are where I took a pass with my brush for contrast.

 

[JamesW]

It looks black in the pictures.

However, if you are seeing green, brown or yellow, it is probably mustard algae.

 

[Winstonselect848]

It looks black in the pictures.

However, if you are seeing green, brown or yellow, it is probably mustard algae.

appears to be brown and very fine.

 

[Texas Splash]

Nothing else in the area around the pool? Trees or storms recently?

 

[Winstonselect848]

Nothing else in the area around the pool? Trees or storms recently?

Couple trees 25ft away. Big Laurel about 10ft away. But never have much in the pool as far as trees go.

 

[JamesW]

Probably mustard algae.

I would do a full SLAM.

 

[Winstonselect848]

Would Mustard Algae have an effect on OCLT?

 

[Texas Splash]

Would Mustard Algae have an effect on OCLT?

Technically it should not. I say that because we know that with any algae, including MA, we first need to complete all 3 SLAM criteria which includes the OCLT. Having passed the OCLT, if one did have a MA, their final step is increasing the FC to the MA level for 24 hrs. After that 24- hr period, there is no second OCLT. The elevated MA FC level is simply insurance to ensure the super-chlorinated wat removed any residual MA spores.

 

[mknauss]

After reviewing some post in the forum I chose to do an OCLT, Over Night Loss Test. I tested @ 6ppm FC last night at 830pm and 6 ppm this morning at 6am. CC is always .5 or 0.

You passed an OCLT with what you see as Mustard Algae. I doubt that should happen.

 

[JamesW]

Would Mustard Algae have an effect on OCLT?

With small amounts of mustard algae, it is not unusual to pass the OCLT.