Algae? Mustard Algae?

Jul 13, 2015
29
Southeast Michigan
My TF-100 test kit is coming today so I can have readings later but I am wondering how I should treat this problem. I have crystal clear water but keep getting these spots on the bottom (see picture). They are brownish and sometimes have a greenish border. When I'm in and touch one with my foot it dissipates. When I brush the spots, it creates a brown/green puff. I put a skimmer sock in and that turns greenish. I don't see anything on the walls at all. Is this regular algae? Mustard algae? I should also add that last weekend (prior to my TFP days) I put in 2 bags of shock from the pool store and a quart of algaecide. After doing this, when the clear cover on the pump was turning green. I took it all apart to clean it. I had this problem last year too but not upon opening this year.

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Based on your description, I would tend to think that is regular algae and not Pool School - Mustard Algae. Regardless, the initial treatment would be to follow the Pool School - SLAM - Shock Level And Maintain anyways. The only difference is that for Mustard, after passing the regular SLAM you take the FC level up higher for 24 hours. But I would follow the SLAM link noted and ensure you complete everything listed on that page. You should be fine and hopefully it won't take too long since your water is in fairly good shape anyways. Good luck, and have a great day.
 
You can swim in the water up to your SLAM. Example: If your SLAM is 20, then you can swim up to FC 20. Once you go over that, it's best not to go in unless you have to do maintenance (i.e. scrub something). At this time, you might not want to wear your newest, best swimwear .... just in case. :)
 
If it were mostly only on the shady side of the pool then it might be yellow/mustard algae, but given its location it's more likely to be regular green algae. Or since you are capturing it in a skimmer sock it could also be pollen. With what you capture in the skimmer sock, feel it. Is it squishy or slimy? Squishy is more likely to be pollen; slimy more likely to be algae. If you have a microscope you can look at some and it will be obvious since pollen is solid, usually round and sometimes with spikes while algae is usually oblong and is translucent.
 
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