Re: Mustard Algae? Or chemical stain?
Hi swimdaddy,Originally Posted by swimdaddy
Yes, I thought as much but I've seen black algae so embedded in a wall that not even a metal brush can dislodge it. Also read accounts of mustard algae, often described as powdery and easily scattered like a cloud of dust but keeps coming back. I can only share my very recent experience which may or may not be relevant. (This is a slow forum, so why not?)
Nine years of pool ownership and I thought I would never see an algae outbreak in my pool ... but it happened for the first time this year. I'm not an expert on types of algae but I'm fairly practiced in its eradication (in other people's pools, of course.) When you see pool water that is not as reflective as usual or has a slight green or greenish-blue cast, or a surface (skimmer wier or pump basket, a shallow step or return jet) that feels a bit slippery to the touch, then the diagnosis is easy. Some type of green algae is spreading rapidly. But other forms are less obvious in their approach.
My 9-year boast came to an end last month for many of the same reasons other pool owners get into trouble: a combination of factors that included the encroachment of large trees that littered the pool with insects, a dirty cartridge filter, extended periods of low chlorine, and general neglect that extended to failing to brush the pool as frequently as I had in the past, and the gradual aging of equipment (rough surfaces, loose fittings). I knew chlorine demand had been increasing over the months but I didn't take any corrective action.
First sign was how annoyingly difficult it was to keep the spa clean. Then I had to acknowledge that the marcite plaster wasn't as vanilla-frosting white as it had been. Soon after I recognized black algae (spots) in the crevices of the tile in a few locations around the pool... challenging but doable with a SS brush.
I tried to remove a very slight "stain" (it looked like rubbed-in yellow brown dirt) that on closer inspection seemed to be everywhere but was most apparent in the deep end (shaded area). Lots of scrubbing and bleach and it didn't even fade much less disappear. It comes close enough to the description of mustard algae—it could be a different species, I don't know, but it motivated me to action.
Increased chlorine demand, coupled with perfectly clear water and a growing generalized discoloring of the walls and floor that wasn't a metallic stain. Hanging over the side of the pool, I could see that if I focused on a tiny area I could just manage to clear a spot with great effort and a tri-chlor tab.
Anyway, this wasn't meant to become the novel that it has become. Since then, I have done all the things I should I have done earlier this year: cut back the trees, cleaned the filter, brushed the pool, increased filter time 25%, experimented with shock regimens—low pH ~7.2 to 7.5 with large and frequent applications of fresh (date-selected) 10% sodium hypochlorite works as advertised! I think I was up to 70% of CYA for a while. At CYA of 35-40, I'll swim when FC is less than 12 ppm so that's my new target maintenance level.
I waited far too long. I'm actually replacing the plastic fittings that can't be made right after soaking in a bucket of 5% bleach all day and then scrubbed. Main pump filter basket, two eyeball returns and a float for the automatic pool sweep, so far. I haven't yet pulled out the light niches but that's next. Just hope that judicious applications of chlorine will disarm anything growing inside the PVC pipes. But the pool looks almost like it did when I first filled it in 2007. 🙂
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I think everyone who owns or is responsible for a pool is still learning. There are just too many fields of knowledge required for any one individual to know everything... plumbing and hydraulics, electrical, chemistry, materials science, etc.
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