Hi, new to the TFP site and forum. Nice forum...many thanks to all who participate.
So, my overiding question is "Does HIGH CYA Cause Mustard Algae in what Otherwise Appears to be a Well Balanced Pool ?????
In early June I went away for a week biz trip and got back to find a significant Mustard Algae Growth. I balanced and shocked before left as I always do...took the pH to around 7.2 and FC up to about 15+...I usually do this before I travel.
Upon return it was pretty bad after only 7 days. Pool water looked like the green Gatorade, only a darker green. Yellow-green "dust" the color of Gulden's mustard on the walls and floor, especially the "shaded" side walls of the pool. So next morning I shocked heavily at sun up with 40-50 oz of 68% cal-hypo, brushed, filtered and back washed 3-4x during the day, added 32 oz of 60% PolyQuat Algecide at nightfall, and then took the pH down to 7.0 at about 10 PM. Filter ran night...thought about a floculent...but didn't add that. The pool water looked much better next morning. A lot of junk settled on the floor...Vacuumed what was on the floor to waste and thought I had "won"....as it was a major overnight improvement.
Well...It just keeps coming back now about every three days. I'll get a thin coating of the yellow brown dust on the floor and less on the walls, vac to waste, and the next 2 days there it is again.
During all this....I'll test the H20 often, 2x/day...typical numbers are pH around 7.4 - 7.6, I keep the FC up above 3, typically higher like 6. Cal 320, TA around 90.
I think I figured out my problem....looking for some agreement here:
I learned my CYA is 89. My kit does not test for CYA...
I think I EITHER screwed up and put too much powdered stabilizer when I opened the pool in April when I was told it was close to CYA=ZERO by the pool store (probably false reading)
OR the stabilized 3" tabs are adding too much CYA (or both).
I'd like to hear some PRO opinions before I drain out 40% of my pool water to get CYA down to 40 ppm.