Algae Colony That Needs to Get Fire Bombed

[apwelb]

So, CYA is 40, TA is 110, TC was 6 at 8:00 tonight, raised to 8. pH is 7.6.

Water is clear, CC is 0. I have passed the ONCLT 2 nights in a row but I am still getting a little bit of growth on the shady side of the liner. It appears about every other day, I brush it off and it doesn't cloud at all. I am puzzled by what is going on.

So, my thoughts are that I have not killed all the algae and that I have a colony somewhere that is still active. My question at this point is will I mess something up if I pull the the frame on the front side of the 2 skimmer boxes off, pull the circular finisher off of the light eye, and pull the trim off of the outside of the ladder steps.

Any other ideas where the algae could be hiding and what can I remove, structurally, in a vinyl lined pool without causing myself problems? I am fine with shocking again, but am puzzled by the fact that I pass all the criteria for being finished shocking (or, as I think about it does having growth on the liner indicate I am not done shocking even though the water looks great, passing ONCLT and no CC???)

Thanks for your help.

 

[duraleigh]

Yeah, that is a little unusual but not unsolvable. I would suggest that you maintain an FC level around 10ppm for the next few days and brush the pool daily even though you may not see the algae every time. That's a simple, pretty cheap "fix" and I think it will work.

 

[JasonLion]

Having visible algae means you are not done shocking, regardless of any of the other results. Algae that manages to form a biofilm on a wall or floor of the pool (what I suspect from your description) can be resistant to normal FC levels, and needs to be brushed vigorously while at shock level.

 

[apwelb]

OK. Thanks for your replies.

Wife and kids are heading out of town until Monday so I will crank up the Cl and brush it like it's my job this weekend and see what happens.

Like I said, it is odd because the water is sparkly and looks real good. It has had lots of use the last 2 weeks and I am only losing around 1.5ppm during the day light hours which given sun and bather load does not seem excessive. Do you guys agree with this statement, in lieu of the ONCLT?

 

[duraleigh]

It probably hasn't been brushed as energetically as it could be. As Jason said, most species of algae can form a biofilm that offers them some protection from the chlorine and brushing it exposes the algae to the chlorine and kills it.

This time of year I will sometimes let my FC level slip and get mustard algae. While elevating the FC level is the first step, the second step to get rid of it is a thorough brushing of the walls and floor.