Does my pool have mustard algae?

[Amrie]

My pool has fine dust all over the bottom, not just in shady spots. It vacuums easily but returns.

This started about three weeks ago. I vacuumed twice and it returned within a day. I did the overnight test and did not lose any FC at all. CC was 0. So I figured it was dust/dirt (we were in a severe drought plus seeing the Sahara dust cloud as super orange sunsets).

Then we got cool weather, so I ignored the pool the last couple weeks other than to make sure the SWG was still plugging away. Water temp mid-70s.

Yesterday was hot, so I netted out a million leaves, vacuumed (to filter, not waste) and enjoyed a swim. Water was sparkling as always. I could see underwater same as above water. FC was 3.8, pH was 7.7ish. CYA used to be 50 but Helene dumped several inches of rain on us, so probably down a little.

Today the water was dull, not sparkly. That's a first! I can see the bottom, but things are noticably hazy when I'm underwater. Dirt was back on most of the bottom. There was some of the "dust" in the skimmer, and it was pea green and more runny/slimy than dusty on my fingers. Chlorine still 3.8.

I'm so confused! It's not in the shade, and it's not on the walls except in a small ring at the very bottom. I've read it "clings persistently" to walls, steps, lights, etc, but this doesn't cling at all. It billows away if the water moves. It doesn't seem to be eating chlorine. Is it mustard algae? Maybe it's just decayed leaf litter?

My plan is to do the overnight test again tonight, and vacuum to waste tomorrow. If I lose FC or if it comes back again, I'll slam and then mustard algae slam. Open to other suggestions. Just confused about the nature of mustard algae, I guess... does it cling to walls or billow and vanish at the slightest disturbance? Shouldn't it always "eat" chlorine? Is it possibly already dead and just recirculating through my sand filter? Gonna be sad if the last few days of swim weather are spent slamming

 

[PoolStored]

If I lose FC or if it comes back again, I'll slam and then mustard algae slam.

The best help we can provide on Mustard Algae is for you to post pics.

Start with the SLAM process...Link-->SLAM Process

When you pass SLAM, then follow the Mustard Algae protocol:

Mustard Algae

Today We are going to show you how you can get rid of mustard algae in your pool. By following the steps in this guide and with no expensive chemicals.

www.troublefreepool.com

 

[Amrie]

Slammed Sun, Monday, and today. Disassembled and scrubbed the skimmer, etc. Got the last of the visible dust out this morning. Brought FC to 30 after the sun went down, threw brush, net, etc into the pool to sterilize.

I'm still confused though. All along, even before starting to slam, there was no FC lost overnight and 0 CC. That points to dirt or pollen, yes?

The dust billowed into a puff of "smoke" when disturbed, and when I brushed the pool during slam, billowy white clouds rose up around the brush, even if the bottom of the pool looked clean. Saturday (day before slam) the water looked hazy and dingy. The gunk collecting in the skimmer felt slimy between my fingers. All that points to algae, right? Did I just catch it while it was still too early to impact the test kit?

I've read mustard algae "clings persistently to walls." Maybe I'm misunderstanding that, but that seems to describe something that's difficult to brush off, like you can scrub and still see some left. That does *not* describe whatever is in my pool. Neither does the part about preferring shade.

Anyway, whether it's the brushing/backwashing/rinsing, the lull in leaves dropping, or the eleventy-thousand gallons of added chlorine, it looks better for now.