I'm another one doing battle with this beast. I am in my third year with a 22' Sofpool and until now the only problem I've had is iron in my well water, which I've been able to manage with metal sequestrants. (Or chelators? I confess I'm not clear on the differences or which I've been using -- probably, I suspect, some of each.) The first year with the pool, I used some kind of expensive chlorine-substitute (Soft Swim, maybe?) from the pool store. It worked fine but cost a staggering amount of money. That winter I found Pool Forum, learned that I didn't need to mortgage my first-born to the pool store, refilled the pool with new water in the spring, started over with BBB and happily used it all summer with a sparkling clear pool.
But THIS year got off to a bad start. Explaining how it happened is too long a story to tell, but to keep it short, we ended up having to refill the pool again, and this time it took me a long time to get ahead of the iron. I deferred adding much chlorine while I worked on clearing the iron because I didn't want coffee-colored water. When I got ithe water blue, there was yellow-brown powdery stuff in the bottom of my pool. I thought it was precipitated iron (I didn't know that mustard algae exists.) So I held back on chlorine for a while longer while I tried to adjust what I still thought was a metal problem . . . until I realized, too late, that the dratted yellow-brown stuff was GROWING.
By now I am quite sure, sadly, that it is algae and not pollen. It behaves exactly like everyone who describes mustard algae says it behaves: it grows on the sides of things, it likes the shady parts of the pool, it collects in depressions in the pool bottom, it makes yellow clouds when I brush it, and worst of all, every single time I get rid of it, it comes back. I am starting on another campaign today to get rid of it, based on what I've read here. I vacuumed and brushed and shocked yesterday. Today the water is blue and clear and sparkling but sure enough, when I brush the bottom there are clouds of yellow and I know if I let those CL levels drop at all, it'll be back. I think I know what to do, based on the other posts in this section. But I do have a couple of questions.
First, I am not entirely sure of my CYA level. I have a Taylor K-2005 test kit and the scale on it for CYA stops at 30. I apparently have less than that: the black dot disappears when the water level has just reached the very top of the tube. Do you think that means my CYA level is 20? That would be about right for the amount of stabilizer I added earlier this summer. Should I add more now? Or is it just as well that it's low while I'm fighting off the dratted algae, since that means the chlorine will be more effective?
Also, I have a resin ladder that is full of nooks and crannies that I can't reach with the vacuum or the brush. I can see yellow stuff in there. I am afraid it will re-infect the pool. Would it be best to leave the ladder in place while I'm shocking, then get it out, take it apart and get it clean before putting it back in? Or should I do that first?
Has anybody out there actually vanquished this stuff once and for all? I would love to hear about it. I need a dose of hope!
I know you'll want a full set of numbers. I'll post them shortly, after I do another test -- thanks!!