Need quick confirmation that I'm dealing with iron

[PoolDoc]

I'd probably start with 20 ppm (50% of CYA) and see if that works.

[jenmenke]

Ah! Now I get it: 50% of the CYA number is the shock level. thanks for saying that.

Here is an odd thing: I'd had the orange stuff on bottom and corners for a couple weeks before I posted here. Brushed, vacuumed, etc. Did one shock treatment, but only brought the chlorine to 15. Orange showed up again and then I posted, as I thought it might be iron. After doing your test with the trichlor tab in the corner where orange was, it all disappeared. No more evidence of orange. That was -- what -- 4 or 5 days ago? I have yet to see anything come back -- and I never shocked again.

Isn't that weird? I'm still waiting for it to re-appear... But don't you think I should wait before dumping all that chlorine in if I don't have to? The water looks perfect...

[PoolDoc]

50% of CYA is usually higher than you have to go.

But, mustard algae is tricky -- I'd recommend holding chlorine at a higher than normal level AND CONTINUING TO BRUSH regularly for at least a week after you think it's all gone.