So with an SWG and a CYA of 80 ppm, you need to have the FC be at least a minimum of 3.6 ppm (4 ppm is a little safer). This is lower than Ben's minimum but we've seen that SWG pools can get away with a somewhat lower minimum due to the more consistent dosing. Definitely only having 1-1.5 is taking a chance for algae to grow unless you are lucky and have low nutrients (phosphate or nitrate) or are using a supplemental algaecide (at extra cost).

Richard