Black Algae in Vinyl Liner

[ASP Asheville]

Hi! I have a vinyl pool that appears to be showing signs of black algae, I have read some topics relating to black algae but it seems most of the cases involve a gunite pool. Is my best option still to shock and brush or are the soft bristles of the vinyl liner brush not going to be effective?

Thanks!

 

[Melt In The Sun]

ASP, can you post some test results? Black algae is not a common problem in vinyl pools, since it can't dig itself into the surface like it can with plaster. Stains from organic material can be mistaken for black algae, and seem to be common in under-chlorinated vinyl pool.

 

[ASP Asheville]

I have a taylor k-2005 kit

ph-7.4
tc- 2.0
fc-2.0
cc- 0.0
cya - <30
alk-50
calcium hardness- 240

 

[teapot]

I think we need pictures, very unusual as stated

 

[ASP Asheville]

 

[ASP Asheville]

it has been spreading up the side of the wall in the deep end

 

[Bama Rambler]

That doesn't look like black algae to me. I however, don't have a lot of experience with black algae. What happens if you hold a chlorine puck on it?

It looks like a product of poor circulation in those spots. Raise the FC level and a good brushing should clear it up.

What's the normal means of chlorination?
Are you fairly confident of that CYA number?

 

[ASP Asheville]

The normal means of chlorination is a floater with tri-chlor sticks and dumping granular chlorine in the pool. But every week when I return to the pool the chlorine is down to .5ppm or less. For that reason I feel confident that the CYA number is correct.

 

[Bama Rambler]

That makes me suspect the CYA number even more.

If you're seeing an FC of .5 or less those stains are most likely organic.

Double check the CYA number and run an OCLT (overnight chlorine loss test) to determine if it's organics to the extent of needing to shock (I'd probably shock it anyway). Then keep the FC at the target level for the CYA.