Green scum stain

[steveo]

Pool looks awesome now that the TA and pH are in an acceptable level. I have one more issue now that I cannot turn up any info on. The previous owners neglected the pool to the point of allowing an algae/scum line to form around the deeper end of the pool under an overhanging oak (that I have since butchered back). It stained the fiberglass gelcoat a light green. At first I thought it was algae, but it does not brush off, and it is perfect line about 2 -3 inches below where I like to keep my water level. Shock did not affect it when I iitially shocked the pool. Is there a way to remove the stain?

My numbers are
FC: 4-7
CC: consistently 0
pH: 7.4 (I am bringing it up to 7.8...it has remained constant since lowering the TA)
TA: 80
CH: 280
CYA: 50

Numbers come from a TF test kit.

One more question: Are all spa lights universal as far as fitting in an underground niche? I have a spa sized niche that accepts a SAL (I called Pentair) but I need to know if a Hayward colorlogic will fit in there too.

Thanks!

 

[duraleigh]

I would suggest you leave your pH @ 7.4.......I see no reason to raise it.

Secondly, assume the stain is organic (almost 100%) and keep your FC a little high for the next couple of weeks say up aroun 8-10ppm. Add enough water to the pool so the stain is completely immersed in the pool water and see what happens. Don't expect it to go away overnightbut I suspect it will diminish or disappear after a couple of weeks.

I cannot help with the lights.