having possible mustard algae problem 3 weeks now

1. Order the Taylor kit; using successive dilutions with distilled water, I validated it against the AquaCheck kit, and they correlated well at the lower levels. I'm guessing the Natural Chemistry kit is bogus. Remember, they'll sell more if it consistently reads high! http://pool9.net/tk/.

Tip: get some sticky putty (Scotch brand @ Walmart) to hold the Taylor test cylinder. It's really tall and easy to tip over. A bit of sticky putty to set it on will make the test go much more smoothly. And use a TIMER for the wait period -- otherwise it's too easy to get impatient.

Regarding the powder - I haven't re-read the whole thread: did we ever suggest, or did you ever do the DE test? It would confirm or eliminate the filter as a source of problems. Plus, if you hand vacuumed the powder while DE was in the filter, you could be sure of capturing the dirt. And, if there is live algae in the pool, it will tend to rapidly stop up the DE and thus your filter, giving another indication. http://pool9.net/de-test/

you had me to do the DE test and none came out the returns.

Sunday afternoon I added 3 pounds of 53% cal hypo and 3 cal hypo tablets to the skimmers.
Monday the FC was 10 ppm.

I intentionally did not do anything the pool yesterday. As of right now, 24 hours later, the FC is 5 ppm.
I have new growth on the shady sides and in the deep end. The brown powder is accumulated on the pool floor, but does not have new growth under it.

I think that the powder is dead algae being returned into the pool.

My question is: where is the LIVE algae? if there was active growth some place in the plumbing or filter then would that explain it? I would figure that algae needed sunlight. We do not have lights in the pool. The skimmers could use a cleaning, but no algae visible there.

If I had to estimate then I would say there is one square foot of visible green algae growth TOTAL in the pool right now. But, I have maybe 5-6 square feet of the brown powder at a time.

Would the drop from 10 ppm on Monday to 5 ppm today be normal? Seems too fast to lose that much chlorine with CYA at 75

When mustard algae is breeding, you will lose chlorine faster than normal.

1. Operate your filter 24/7.
2. Keep your chlorine in the ORANGE to orange-tinted DARK YELLOW range.
3. Add 2 - 3 cups of DE powder after EACH backwash. That will stop algae from leaking through.
4. Brush the algae spots after each chlorine boost.

Where did you get 53% cal hypo? What *else* is in it? What's the brand/product name?