Source of Algae

[chem geek]

Thanks for letting us know the source of your recurring algae. Wow, this stuff is pretty hardy -- I don't suppose there is very much light that gets into the recess behind the light, but possibly just enough to keep it barely alive (clearly, water gets into that niche). This helps explain why just doing the shocking (at higher FC levels than normal shock -- 60% of CYA level after first lowering pH to 7.2) would kill an existing bloom but those with mustard/yellow algae would need to keep a higher FC level (15% of CYA) to keep it away and couldn't use Ben's chart values ("Min" being roughly 7.5% of CYA) or else it would keep coming back.

So when this source of algae finds a niche to live in, it takes a permanent algaecide to keep it away -- either higher levels of chlorine, Borates, and I suspect other algaecides would work as well such as PolyQuat 60. That's also very good information about the Borates keeping the yellow/mustard algae away. I think that's the first report of it being successful against this algae. Is your pool at 50 ppm Borates or some other level (since the recommendation is 30-50)?

Richard

[topless]

I ended up at 80ppm of borates, either my pool is smaller than I calculated or the 2 boxes I put in when I opened it didn't dilute as much as I expected. More likely it's a combination of both. It's a freeform pool and only has 1 side that's straight, it's has curves around the rest with 4 steps in one corner and about 20 total feet of seating. I calcu-guessed 20,000 gallons, but it may be as small as 16,000.

Anyway, after vacuuming to waste this morning, the pool looks as good as it ever has. I haven't found a 300w floodlight bulb yet, so the light housing is still sitting on the deck.

It may be the higher borate level was the reason for the results against the mustard algae. But, I'm no chemist, you guys lose me at times.