Algae growth on under side of spa coping

Pperc15

Gold Supporter
May 17, 2019
346
Philadelphia
Hi all,
Just got into the spa for the first time in a while and found algae growing on the under side of the coping. It’s not on the water line or under the water. My chemistry has been fine and CC has been 0.5 consistently for a while. I’m keeping FC well above minimum but like I said, this is above the water line. Perhaps with water evaporation (pool is warm and air is cold) it’s putting moisture onto the bottom of the coping. So, question is, what is the process for eliminating it?

1. I believe I can drain the spa making it easier to work in there.

2. What should I use to kill the algae? Spray bleach onto it? What concentration? for how long?

3. Brush? Can I use a stiff bristle brush or do I need a wire brush?

4. When can I refill the spa and get thing going again?

Pictures attached. I think it’s dark green. A bit slimy to the touch. Hoping it’s not black...
 

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,378
Laughlin, NV
Hit with some diluted bleach and a brush. Going to take several attempts I would imagine. Stiff brush should be all that is necessary.

I would dilute bleach 4 parts water to one bleach. It will still be able to spot your clothes so wear old stuff.
 
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Pperc15

Gold Supporter
May 17, 2019
346
Philadelphia
Hit with some diluted bleach and a brush. Going to take several attempts I would imagine. Stiff brush should be all that is necessary.

I would dilute bleach 4 parts water to one bleach. It will still be able to spot your clothes so wear old stuff.
Took care of it yesterday. Hit it pretty hard and scrubbed quite a lot and got off all the green. Bits and pieces on the spa steps which washed away when I refilled the spa. Decided to super chlorinate the SWG for 24 hours as well. Any concerns? Should I brush the inside of the spa extra well for a few days?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,378
Laughlin, NV
As long as your FC was at or above target for your CYA in the pool water that little bit of organics should be take care of. Just monitor FC as usual.
 
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