+ Don't use the scale inhibitor; don't buy any more chemicals from them. Do NOT add calcium; scale inhibitor; scale remover, alkalinity increaser or decreaser, algicides, etc.

+ Stay away from BioLab "Alex" testing -- it seems to lead to inevitable overdosing. (Which improves dealer sales -- imagine that!)

+ Read about 'sand algae' => http://pool9.net/algae-s/
Check out the pictures, and confirm that this is your problem.
+ Turn your SWCG off; buy 20 gallons of PLAIN 8% store brand bleach; buy a cheapo OTO/phenol red drops kit; begin dosing with 2 gallons each PM; test with OTO in the AM; maintain DARK yellow OTO results, till there's no trace of algae left.

+ Order a K2006 kit; you'll need one => http://pool9.net/test/

+ Read about lowering your alkalinity, which is what you'll need to do => http://pool9.net/alk-step/

+ Read about handling muriatic acid, which you'll need to use => http://pool9.net/ma/

+ Post your pool dimensions; over 50% of pool owners have significantly wrong estimates of their pool's volume.

+ Brush your pool, to remove any algae films. Vacuum to remove debris and any calcium particles that have collected. Do NOT scrub your pool to remove the 'sand', especially if it's a vinyl pool!

Good luck!