Mustard/green film on walls = algae?

[guydot]

I am still considering myself a newbie, although with the help of this forum I have been taking care of the pool by myself for the second season. My question:

Every week -10 days I see a mustard/green film on the pool walls, mainly in the deep end. It brushes off easily (creates a cloud when brushed). I used the "maintenance" dosage of algaecide occasionally and I do not think I saw any difference.

Is it algae or just dirt? What should I do? The water is pretty balanced, with PH currently at 7.8, as it tends to drift up every couple of weeks.

Thanks!

 

[duraleigh]

Can you post test results?

 

[guydot]

SWG with Plaster:

FC 1.5- 2
pH 7.8
TA 70
CH 220
CYA 30 (I know, this is low)
Salt is at 2800

 

[guydot]

Anything?

 

[frogabog]

With a CYA level of 30, the minimum for your SWG is 2ppm.

Sounds like you're always at or below minimum. My bet is on algae and the need to begin shocking. Do you have a combined chlorine result? (TC-FC=CC).

Your FC level should be above minimum at all times. That means you need room to lose some chlorine if say... the sun comes out or people swim. I'd shoot for 5-6 ppm.

 

[Richard320]

[center:26hxefk4]Aha! I see a clue!

[/center:26hxefk4]

SWG with Plaster:

FC 1.5- 2
pH 7.8
TA 70
CH 220
CYA 30 (I know, this is low)
Salt is at 2800

FC 1.5- 2 tells me you're using the color matching test. And even if it's right, it's wrong. With 30 CYA, normal FC is 2-6. You're below that, so you probably are just barely staying ahead of an algae bloom, and every week or 10 days it gets ahead of you.

You're a prime candidate for the Shock Process. But to do it effectively, you'll need a decent test kit (defined in Pool School) and the How-to directions in

 

[guydot]

Thanks! Sounds like I need to increase the clorine generation from 60 to 80 pervent and add CYA. Is shocking a must in my situation?

 

[Richard320]

Thanks! Sounds like I need to increase the clorine generation from 60 to 80 pervent and add CYA. Is shocking a must in my situation?

I'd say so - you have algae.

Once the process is complete - not before - raise your CYA level up to 70ish, then the SWG can keep up with the losses to sunlight.

 

[guydot]

Just to update and contribute to the knowledge base: it was algae. Shocking once then raising CYA and keeping the FC level at about 3ppm did the trick. I have been algae free for weeks now.