I wonder if some of the problems that SWG owners have encountered with algae at recommeded CYA levels could be to either:
1) running at the low end of the recommeded 1-3 ppm FC levels
2) not keeping a good check on the pH and allowing it to drift upward too much before lowering it?
I maintain my pool at 3 ppm FC and do not let my pH rise above 7.6 (okay, MAYBE 7.8) before I add acid.
Also since my SWG does not compensate for temperature (Goldine Aqualogic PS-8) I do ajust my cell output if I see the chlorine levels are dropping or rising. (my pool has run on as low as 5% output in cooler weather up to 15% recently with my FC going up to 4 ppm)
I do test my water at least weekly (full tests except CYA and CAL) and do OTO and pH testing at least once more duing the week. Perhaps this is the difference in why I have never had any problems with algae. I test a lot of water at the pool store and I see that many owners of SWGs let their pH climb to 8.0 or above and never really get it down to where it needs to be. I also see these people having algae problems in their pools. On the other hand I had several customers with very low CYA (30 ppm and below) that were running their cells at very high output and also had algae problems and cloudy water in their pools. In both cases these people reported back to me that their problems seemed to disappear when their CYA levels and pH were brought into line.