Thanks - I'll try that while I'm waiting for my order to arrive.

Because I had .5+ CC last evening, I put in bleach to what should have brought it up to 15 (although I didn't go out later and check it). But I started at 8 and added about 2 3/4 gallons for a 23,500 pool.

This morning I have:

10.5 FC
1 CC.
Ph 8 (climbing because so much aerating going on?)
Didn't check Alk but I'm sure its still 150+

I added some muriatic acid - Obviously, I'm not in much danger of my Alk getting too low!

I also put in bleach to bring FC up to 15ppm again - I'll test it at about 2 hours to make sure I made it.

The pool still has layers of very yellow (which is obviously pollent), and more silty brown like it had yesterday. Brushed the pool again.

If this does turn out to be mustard algae (and really - I don't know how to tell) I plan to order Polyquat 60 (I order either from intheswim or waterwarehouse - depending on who has the deal at the time.) I thought I'd start adding a maintenance dose to as a deterrent from this happening again.

Am I on the right track?