Small algae bloom in pool


Active member
Apr 24, 2019
This forum has been very helpful to me in past with algae issues. I did a SLAM a few months ago, followed instructions religiously, and was very successful in turning my pool around. Since that slam, I do not introduce any new CYA in pool and maintain a current CYA level of 4.5. I use liquid bleach to keep FC maintained and I use the CYA chart, which tells me I should maintain at least a FC of 7 to stay algae free. That said, as of late, I’m noticing small algae bloom on some surfaces - nothing like before but thought my FC levels would be enough so that it guaranteed no algae bloom?

What am I missing or doing wrong? I use a Taylor Complete FAS-DPD chlorine) kit, test & treat for FC every 2 days and check CYA once/week.


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
We round up. If the dot disappears between 50 and 40 we call CYA 50. Halfway between lines is not 5 since the scale is logarithmic, not linear. Your FC target should be 6-8.

There are no guarantees with algae. Either you did not totally eradicate it during your last SLAM Process or your FC fell below your minimum FC at some point that let algae take hold.

With a FC target of 7 checking FC every 2 days is too long. Your minimum FC is 4. So if your normal FC consumption is more than 1.5 ppm a day then your pool is falling below minimum. Outdoor pool FC consumption is usually 2-4 ppm a day depending on how much sun it gets.