KurtV - I raised ch to at or above 15ppm for a number days and the mustard returned. No doubt the quickly rising pool temp isn't helping.

I guess I can just keep the ch level high for longer, but I doubt if 7 days (random example) will take of the problem if 4 days didn't. Eventually, you've to take care of the problem, so I am resigned to taking the next step - poly quat.

mwsmith2 - interesting you say that about the relationship between the intro dose and maintenace dose. the bottle says 11-17 oz per 10k gallons for intro, but only 2-4 oz per 10k gallons for maintenance.

I figured I'd just go with 25 oz (close to minimum range) and see how it goes.

So, does it matter what your ch levels are when you add poly? My ch level is still pretty from the supercholorination. In fact, despite having algae, my FC has been in the 6-9 range for about a week, and I haven't registered any measurable CC. I would think that with FC that high, it would attack the algae or some other 'goo' and make CC. Especially since I've been brushing the walls, steps and transitions every day for about 2 weeks. Hmmmm....