@BigDave: Thanks!

@BromineUser:

1. Do not chlorinate.
2. Do use HEPD *AND* polyquat. There's nothing special about BioGuard chemicals, except the labels & pricing. Check these at Amazon if you need more.
Kem-Tek 311-6 Pool and Spa 60-Percent Concentrated Algaecide, 1 Quart
Jacks Magic The Pink Stuff 1qt (60% HEDP)
3. Keep the pH below 7.6
4. Brush daily; operate the filter 24/7.

What kind of filter do you have? If a sand filter, get a bag of DE powder, and add 2 cups of DE daily to the skimmer. Watch your pressure and backwash on a 5 psi increase. Do NOT add DE to a cartridge filter!