Algae on Tile Grout Above Water Line

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H

HouTex

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Mar 7, 2011
412
Houston, Texas
I did my annual scrubbing of my pool tile yesterday and what I thought was black scum from dirt/sunscreen/etc. was in fact algae. My pool has always been sparkling clear and I've never had cloudy or green water. I've never noticed any algae in my pool so I was surprised to see algae growing on my grout above the water line.

The stuff was growing on one side of the pool that gets the least circulation (the tanning ledge) and in the spa away from the spill over. The other three sides of the pool were clean and really didn't even need to be cleaned. The stuff looked black but when the bigger pieces broke off I could see the dark green fiberous algae. It looked similar to what sometimes grows on brick siding in high moisture areas. It was very hard and it took a stiff brush with some cleaner to get it off.

I have not been brushing my pool as often as I should so I assume this is the cause. I have always kept my FC in the range suggested in Pool School and the water always look great so I don't think it's a water chemistry issue.

I saw another thread on algae above the water line and there did not appear to be a clear answer as to how or why algae would grow above the water line.

Any thoughts? Should I be concerned? I plan to brush the pool and the water line tile more often (like I did the first year when I brushed it every week).
 
I have the same issue with algae above the waterline, but now it has started to move below, as well. The common threads among similar posts I have seen would suggest you/I/we have not been brushing as often nor completely as we know we should. The condition is worse where there is less direct light. It is also worse in corners that are difficult to reach. I have had problems with high CH and scale at the waterline, too.

The one thing I would like to know is whether the algae can survive inside the grout when sprayed with bleach and brushed. There seems to be a slight discoloration left over after brushing. Do you get this staining in the grout, as well? Should I consider removing and replacing the grout where a slight stain remains?
 
IMG_0513.jpg
I searched the forums trying to find a good picture of what some people were trying to explain about the above waterline algae growth but couldn't find any. Since I have recently encountered the same issue, I wanted to post a pic of it. This pic is actually an anomaly. It was the only place I could bend over backwards and snap a pic without getting in the pool but although the algae is growing below the waterline, 90% of the rest is above the water line.

I brush my pool twice a week and vacuum once a week, always cognizant of the tile line. My normal pool chems are as follows:
FC 8.0
TC 8.0
PH 7.5
TA 90
CYA 80
CH 300

I seem to have persistent algae problems if I miss a brushing or chlorine level drops a bit. Maybe because the algae is living in the tile but I dont know how to keep it at bay. My sanitizer wont work on something it isnt touching. How the heck is the algae growing above the water line?

Yes I know my CYA is a little high. I try to keep the chlorine levels up to match but here in south florida you need higher stabilizer and chlorine because the sun and heat destroys it fast. Any ideas? Thanks
 
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