Adjust TA when chlorine very, very high?

[chem geek]

Patience, patience, patience. Yes, it can take some time to kill off a lot of algae. At least it's getting better, so stick with it. With your CYA of 50-60, I wouldn't go above the FC level of 40 since that should be enough to zap even this hearty algae, and it sounds like it is. At this point, just wait this stuff out keeping the FC at the high level. Don't worry about adding any more acid at this point -- your dropping TA could mean that your pH isn't really as high as you think (due to high chlorine and extra thiosulfate drops) and when the chlorine level drops back down (after you've conquered your algae problem), the pH will drop anyway. Just add the baking soda to bring up the TA again (I wonder if the algae is consuming the carbonate???).

And hang in there -- you are on the right track! Oh yes, with this much junk you are killing in your pool, you will probably have a lot to vacuum out and/or to clean out of your filter. You might check your pressure to make sure you haven't caked your filter with this stuff.

As for algaecide, some people have reported success using 60% polyquat algaecide, but this is best done BEFORE the algae starts -- as a preventative -- so would be something you would add before August each season since that is when people first start reporting this hard-to-kill yellow/mustard algae (which sounds like what you might have). Perhaps keeping higher chlorine levels would also prevent this stuff, but we don't know enough yet of how high that would have to be (i.e. is the high end of Ben's chart good enough to prevent this stuff???).

Richard