We have a frequent issue with yellow algae in our above ground pool, despite the fact that the filter runs 24 hours a day, there is always chlorine in the skimmer, and we shock each week. I treated it yesterday with algaecide, but it is still there. Here are my test strip results: FC, 5; Alk, 120; pH, 7.2; CyA, between 100 and 150. What am I doing wrong?! Thanks.
It is likely that you have one of two problems. 1) you may have a dead area where there is no circulation and therefore chlorine is not reaching this spot and algae is starting there and spreading even into treated areas. Or 2) you have holdover algae somewhere else. Could be that it is resident in a dirty filter or that there is a porous area of your pool that would require scrubbing to remove the entrenched algae.