Wow...... That's an amazing reply! Thank you so much for taking the time, energy, and thoughtfulness to put it together.

You are right about having a chlorine demand, I do, and there are details below if you're interested in how broke I am trying to fix it. :-)

I will try to find somewhere that will sell me a trunk-load of regular household bleach. My pool guys say that I have to add the demand-dose all at once or it's a waste as small doses will be ineffective. Is this true? How do I decide how much bleach to use?

Just for background, I have around a 30,000 gallon vinyl-liner pool. I had perfect sanitizer readings between 2-5 from opening through all summer adding 6oz of metal magnet, 6 oz algaecide, 6 oz clarifier, and 3 lbs of oxy-sheen each week.....until two things happened three weeks ago. One, my automatic pool cover broke so the pool is exposed to the sun and two, I left town for a long weekend. When I returned, my sanitizer readings were zero.

I have hardly had ANY swimmers this summer due to our cold temperatures. All were adults except for a total of 10 hours by some pee-respectful 12 year olds. (No ammonia shows on pool sample tests). My algacide levels are so high that the store recommended I stop regular maintenance for a while; same thing with my sequest (metal magnet). And yes, we have checked the sand and filtration. The water is clear and looks perfect except it doesn't have that sparkly shimmer when the water is absolutely perfect.

So according to what you said, the problem may very well be a combination of sun and algae. If it's algae, then with my algaecide levels so high and the amount of chlorine I have already put in, it must be an invisible and indestructible algae!!!

Now want to hear about what a money-maker I have been for my pool store? In their defense, they told me the bit about how testing for chlorine/bromine (sanitizer) works as well as the bit about the presence of chlorine in the bromine tabs. Also, when they built the pool, I was the one who asked to use bromine as my son used to get rashes and huge rings around his eyes whenever he was in chlorine pools and our doctor said it was an allergic reaction. Anyway, here's my life for the last three weeks:

-First we used 12 plus lbs of Burn-out 35. Back to zero within 3 days.
-Then we used 24 lbs of Burn-out 3. Back to zero within a few days.
-They did a chlorine demand test which called for 54 lbs of Burn-out. I used 64 lbs. Sixty-four! Back to zero.
-Another demand test still called for over 50 lbs of Burn-out. We used 40 gallons of their liquid chlorine (around 12% or something). Back to zero with the same demand.
-Then they GAVE me 20 gallons of liquid. Back to zero with same demand.
-Then they ran a phosphate test with results of almost 1000. I used Bioguard's pool tonic (also on the house). Still almost 1000.
-Then I used SeaKlear's phosphate remover that was supposed to be stronger and cost around 50 bucks! You guessed it, still 1000 and my chlorine demand remains.
-The Bioguard rep was in today from Atlanta and he called his chemical guru who said the bit about cya and recommended draining the pool about two feet hoping to get the cya below 25 and then re-running the chlorine demand test.