Richard...thank you for your reply. Your chart, in another thread, is what's prepared me for the chlorine levels I'm now using - but I'll get to that.

My drop in TA on 9/13 was measured at a ph of 7.8, my previous "normal" of 80 throughout the summer was at a pH of 7.5. Just prior to the 9/13 tests, actuallly on 9/7, I ran a pH test with the Wally World HTH kit and also with the Taylor reagent from Ben's kit. With the same water sample, the HTH measured 7.5, as it had been for nearly the entire summer but the Taylor measured 8.0, maybe higher. The HTH kit HAD measured higher pH values accurately (I'm assuming) in early summer when I first tested my new pool's water.

Since then (9/7), I've been adding small amounts of muriatic acid every few days, if not almost daily and have yet to see a nice solid 7.5, as this summer. I recorded today's test at 7.5 (almost) but with no MA additions today, I'll bet tomorrow it'll be at least 7.8.

Looking back, maybe all my TA drop is from the additions of muriatic acid. After running such a stable pH all summer, I haven't had to remember that concept because I added so little MA all summer and my TA stayed right at 80.

Outgassing...I do have a waterfall that, previous to this algae, had been on 12 hours a day. I had absolutely no problems with stable pH during the summer. The only change I made in early September was to run the pump (and waterfall) for the majority of time in the daylight, rather than overnight and drop the time to 10 hours. Right now the waterfall is off to make sure all water is running through the filter.

My CYA measured 50 or slightly higher on Monday's test. Like most new pool owners, I struggle with consistency - at times, I've measured it at 40. I did recheck and can say that I've added 10# of CYA since the pool was finished in June. With no draining or backwashing (cartridge filter) a CYA of 50-60 is probably correct.

Your chart, comments, and the experiences of other forum members have helped a great deal, as I would have never expected to have to go over 20 FC to clear up my pool. Not that it's clear....yet. Going to 35 or a little higher MAY have been just the ticket; I'll know more in the morning when the light is better. Having never had algae and having never had a pool before, I still can't say for sure that algae is what this is...but it's my working theory.

IF both pH and TA should return to lower levels when the chlorine returns to more normal levels, what do I do in the meantime? Do I just keep trying to keep pH and TA somewhat in balance while my FC is so high?