Algae chunks growing between pool tiles

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K

karasdad

Member
Feb 13, 2024
7
Hawaii
Pool Size
17000
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Hello,
I am having a problem with algae chunks growing between the tiles of my pool. The water is otherwise clear and there is no film on the walls of the pool. It seems to be spreading, even though the FC is 6 and I have been running my SWG at a much higher level and for longer than is typically required at this time of the year. I will also find these chunks (bright green to dark green) when I scoop leaves off the bottom of the pool. The chunks won't come off with a normal pool brush, but will come off fairly easily if I use a stiffer scrub brush while snorkeling. I bought this house (in Hawaii) 4 years ago and the grout was in pretty bad shape (or non-existent in some parts) when I bought it but did not see these chunks until this summer (I would brush them out by hand). I thought I had stopped it this summer, but it has come back this winter. I have included pictures below.

Questions:
1: What type of algae is this?
2: What is causing this growth?
3. How do I stop this and prevent it from reoccuring?
4. Am I screwed until the pool is regrouted?
5. Is it safe to use a stainless steel brush on tile? I would like to be able to brush without entering the pool?

CYA is between 40 and 50
FC is 6
PH 7.4
Alkalinity 100

Thank you for your help.

EDIT: I attached 2 additional photos taken with a better camera.
 

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Last edited:
karasdad said:
Hello,
I am having a problem with algae chunks growing between the tiles of my pool. The water is otherwise clear and there is no film on the walls of the pool. It seems to be spreading, even though the FC is 6 and I have been running my SWG at a much higher level and for longer than is typically required at this time of the year. I will also find these chunks (bright green to dark green) when I scoop leaves off the bottom of the pool. The chunks won't come off with a normal pool brush, but will come off fairly easily if I use a stiffer scrub brush while snorkeling. I bought this house (in Hawaii) 4 years ago and the grout was in pretty bad shape (or non-existent in some parts) when I bought it but did not see these chunks until this summer (I would brush them out by hand). I thought I had stopped it this summer, but it has come back this winter. I have included pictures below.

Questions:
1: What type of algae is this?
2: What is causing this growth?
3. How do I stop this and prevent it from reoccuring?
4. Am I screwed until the pool is regrouted?
5. Is it safe to use a stainless steel brush on tile? I would like to be able to brush without entering the pool?

CYA is between 40 and 50
FC is 6
PH 7.4
Alkalinity 100

Thank you for your help.

EDIT: I attached 2 additional photos taken with a better camera.
Click to expand...
What has the FC level been over the last few weeks/months?
 
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Note that algae growth is due to insufficient chlorine.

So, while you might think that you are providing enough chlorine, you are not.

The grout does make the problem worse because black algae is protected and grows protective layers that insulate it from chlorine and from light brushing.

Brush - a lot and keep the FC higher.
 
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Is your pool a tiled pool?

Is this stuff growing on tile in the pool water or above the pool water?

Put a better description of your pool in your signature.
 
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SLAM Process
You mentioned grout issues. Are you saying that there is no grout? Or that it’s growing in places where the grout is gone? Maybe this space is providing a nice home for the algae? Seems if you can’t get ahead of this by maintaining higher levels of chlorine and scrubbing, you may need to regrout if you can.
What have you kept your Chlorine at? Have you done a slam?
 
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@Katodude has experience with black algae and good advice in this thread…

Black algae

Update. I contacted the pool company. not a retail pool supply store- the people who built the pool and maintain my equipment. They confirmed most of what I found here with one difference. they don’t use liquid chlorine or household bleach. anyof those supplies are too old by the time they get...
www.troublefreepool.com www.troublefreepool.com
 
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ajw22 said:
Is your pool a tiled pool?

Is this stuff growing on tile in the pool water or above the pool water?

Put a better description of your pool in your signature.
Click to expand...
Yes, it is a tiled pool and the stuff is only growing in the pool water. Thanks for your help.
 
kul said:
SLAM Process
You mentioned grout issues. Are you saying that there is no grout? Or that it’s growing in places where the grout is gone? Maybe this space is providing a nice home for the algae? Seems if you can’t get ahead of this by maintaining higher levels of chlorine and scrubbing, you may need to regrout if you can.
What have you kept your Chlorine at? Have you done a slam?
Click to expand...
The grout is missing in some places and in poor condition in others. I am planning to have it regrouted but was hoping to wait until my wife has the pool deck redone to provide wheelchair access for her parents (she is planning for the next year or so) to avoid emptying the pool more than once. It does seem like there is very little margin for error with the grout. I started a slam last night. Thank you for the reply
 
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JamesW said:
Note that algae growth is due to insufficient chlorine.

So, while you might think that you are providing enough chlorine, you are not.

The grout does make the problem worse because black algae is protected and grows protective layers that insulate it from chlorine and from light brushing.

Brush - a lot and keep the FC higher.
Click to expand...
Yes, I'm sure I had insufficient chlorine for a while. The FC level seemed fine and there were no signs of algae until a storm filled my pool with leaves ( and a power outage knocked my SWG out for a few days) while I was away for a week. Not enough to turn the pool green, which is all that I was really concerned about until I learned until black algae. The algae has slowly been getting worth since. In your earlier post you mentioned to brush with a plastic brush. I currently use a wall whale, which has a hard time getting the algae out between the cracks. Is there a better brush to use? When I saw a small patch in the summer, I was able to use a scrub brush while snorkeling, but am unable to now because it is cold and the spots are deeper. Thank you for your help.
 
Last edited:
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I would like to thank everyone for their help. I was told that it wasn't black algae by the pool store and the neighbor's pool service so learning that it actually is helps a lot. It's not great news, but at least I can deal with it now. I stopped too early last time thinking it wasn't black algae and allowed it to come back. One problem I have is that my current brush, a wall whale, is unable to get the algae out from between the cracks. Does anyone have a recommendation for a brush that would work better? I used a scrub brush and a snorkel to deal with spots in the past. But the pool is still cold and the spots are deeper than in the past.
Again, thank you all for your help. This is a great site.
 
Oof, this is a tough one. Normally I would tell you to get in the pool with a pressure washer to blow out the black algae. I just have no idea what a pressure washer will do to your grout. I would be scared to pop out tiles. I also dont know what kind of brush is going to get into the grout enough to scrap out the BA.

I think my best advice is to get into the pool with a bamboo bbq skewer and scrape out what you can. Then get in there with a 1 gallon pump sprayer with the strongest liquid chlorine you can find and blast those spots.
 
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Katodude said:
Oof, this is a tough one. Normally I would tell you to get in the pool with a pressure washer to blow out the black algae. I just have no idea what a pressure washer will do to your grout. I would be scared to pop out tiles. I also dont know what kind of brush is going to get into the grout enough to scrap out the BA.

I think my best advice is to get into the pool with a bamboo bbq skewer and scrape out what you can. Then get in there with a 1 gallon pump sprayer with the strongest liquid chlorine you can find and blast those spots.
Click to expand...
Pressure washer is too aggressive.
 
karasdad said:
I would like to thank everyone for their help. I was told that it wasn't black algae by the pool store and the neighbor's pool service so learning that it actually is helps a lot. It's not great news, but at least I can deal with it now. I stopped too early last time thinking it wasn't black algae and allowed it to come back. One problem I have is that my current brush, a wall whale, is unable to get the algae out from between the cracks. Does anyone have a recommendation for a brush that would work better? I used a scrub brush and a snorkel to deal with spots in the past. But the pool is still cold and the spots are deeper than in the past.
Again, thank you all for your help. This is a great site.
Click to expand...
Get your FC up to SLAM level first and then keep it there while you brush.
 
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markdpratt said:
Maybe try a 5” stainless steel bristle pool brush like this one I picked up along the way? Good luck. View attachment 556745
Click to expand...
My concern with using a stainless steel bristle brush is scrubbing hard or over time it can scratch the tiles. Replacing the tiles will be more expensive then the grout.
 
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markdpratt said:
Maybe try a 5” stainless steel bristle pool brush like this one I picked up along the way? Good luck. View attachment 556745
Click to expand...
I’d give it a week or two of SLAM without brushing before I used a stainless brush. The SLAM may take care of lots of that even without brushing. Like said above I’d be concerned steel is to aggressive. Delaying the SLAM will just let it get worse.
 
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A SLAM without disrupting the surface is not going to help with BA. It’s also not going to hurt either. At a minimum I would get the FC level up to 20% of CYA.

I just dont think there is much the OP can do without getting into the pool with a snorkel and figuring out a way to disrupt the BA.
 
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