So this is the 2nd year I've had an above ground vinyl 15' x 48" Intex pool (4440 Gal.), the first year I was able to maintain decent FC levels from the get-go by starting it with just bleach then occasionally adding some dichlor.
This year... different story. After opening it, I struggled a bit to keep FC at 3 or more, having to add a fair amount of chlorine every other day, but the pH was very stable and the water was crystal clear... until now. When levels would get low and I would add enough liquid chlorine to bring it to an FC of 6ppm, then the next day I would measure and the pH and FC were off the charts (FC readings of 8 or more). I was using the pool calculator and using all the correct amounts, however this year I am using 12.5% liquid chlorine instead of 6% bleach and di-chlor (like last year). When the readings were high (8+ FC), I wouldn't add any chlorine at that point, then I would test again the following day and it would be 0-1... finally I came to the conclusion that I obviously needed more stabilizer but still never thought much of it because everything seemed clean and crystal clear.
The pH readings have remained stable every day (7.4-7.6) and like I said the water remained clear until about two days ago... I noticed the water was a tad cloudy and green, and I started getting yellow "dirt" on the bottom surface. After I noticed the cloudy water I immediately sampled all chemical readings and they seemed OK except for low FC and CYA, which I am sure is the root of my problem...
CYA (less than 30, can't read lower)
I went to the local pool store and explained the situation (although I didn't mention algae since I was in denial about having an algae problem until today after doing more research), and they told me the dichlor I was using did not put stablizer or CYA into the water. (I am not even sure if that is technically possible or true, based on last year's experience) So I bought some CYA granules knowing that I for sure needed CYA and started floating them in a pair of tights tied near a return yesterday.
Anyway, today, I go outside to check the pool and see if the water looked any more clear (I added some chlroine last night [enough to get to 6 FC] and have been running the filter constantly), and it actually seems the same or slightly worse with the yellow stuff reforming on the bottom. Basically, I am unusure how to move forward from here... I kinda wish I had explored algae being my problem a day sooner, but there's no going back now. I am in a bit of a panic and was hoping somebody would have some advice... some thoughts/questions:
1) Leave the CYA granules in, since I know that it's needed? Problem is, I don't know my current CYA reading (aside from it being under 30, possibly even 0 since the granules will take a while to dissolve) and not sure when I'll be able to get a good reading. I also cannot backwash my filter for a week with these still dissolving. (I am using a mid-range Intex Sand filter instead of the cartridge filter I used last year)
2) Start shocking to kill the algae even while the CYA is still dissolving? Or maybe take out the CYA so I can get an effective shock in?
3) Use some sort of algaecide treatment? (I do have some Poly-30 on-hand...)
4) When should I start brushing/vacuuming? Some sources say to make sure not to stir it up, some say to start cleaning it daily?
Any help from the experts would be greatly appreciated to help this newbie through his first algae problem