Mustard Algae??

[CarlD]

Doing GREAT! That's exactly what should happen! Do NOT add the sparkle. You CAN add some Polyquat algaecide, maybe an ounce or two, not more.
Polyquat is sold under all kinds of labels, but the ingredients should be: 60% poly [oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene dichloride] as the ONLY and SOLE active ingredient. It's the ONLY additive I ever use, and certainly the ONLY algaecide. It also doubles as a clarifier.

You can also put a little DE in your filter via the skimmer...Just enough to raise PSI 1 lb, but backwash first.
Also, skimmer socks in your skimmer can pull an AMAZING amount of junk out. I usually can make one last a month, and 3 or 4 go for less than $10.

Carl

[Watermom]

Don't know about the Sparkle. I wouldn't use it.

But, the fact that you had such a big loss of cl overnight says that you need to continue shocking. Continue to do so until you can pass the overnight test.