Mustard Algae?

Shawkr

Member
Sep 9, 2021
22
California
Hi all,
My father who took care of our pool recently passed so I’m coming here for help. We have a large stain on the bottom of the pool. One professional told us it was mustard algae while another professional said it was not. Regardless, I’ve attached pictures and wanted to see what the community thought it was as well as how to remove the stain. Not sure if this is useful but the pool is in California and is salt water.
Any help would be greatly appreciated! C6CDC45A-DF1D-4A4F-8480-B292E1D6E81A.jpeg17EFD77E-3F9E-4A77-BD56-3D9DCDED38CF.jpeg37EB1B81-BD79-4467-9833-D2FEA6A0404C.jpeg8D663A54-827E-4238-982C-050361D487F7.jpeg
 
  • Wow
Reactions: Mdragger88

JamesW

TFP Expert
Mar 2, 2011
28,291
What happens if you brush it really vigorously with a stainless steel pool brush?

How long has it been like that?

Try putting some vitamin C or ascorbic acid on it to see what happens.

What are all of the chemistry readings?

Can you pull the cartridge out of the filter and show a picture of it before you clean it?
 
  • Like
Reactions: Mdragger88

Mdragger88

Bronze Supporter
Jun 1, 2018
3,378
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Until we get some more eyes on it here is some helpful reading about stains & identifying them 👇
 

Shawkr

Member
Sep 9, 2021
22
California
What happens if you brush it really vigorously with a stainless steel pool brush?

How long has it been like that?

Try putting some vitamin C or ascorbic acid on it to see what happens.

What are all of the chemistry readings?

Can you pull the cartridge out of the filter and show a picture of it before you clean it?
We’ve tried brushing with a normal pool brush to no avail. We’ve also tried vitamin C and that didn’t work. Apparently the stain has been there longer than six months. I can try to pull the chemistry readings and filter along with a picture in a bit. Thank you thus far.
 

JamesW

TFP Expert
Mar 2, 2011
28,291
Maybe some combination iron, copper, silver or other metals.

I don't know why it would form in that one spot.

Maybe someone threw something into the water that settled in the spot due to the circulation patterns of the water.

If it was mustard algae, a brush would move it, especially a stainless steel brush. I don’t think that it is mustard algae.

Black algae would be difficult to move, but black algae is actually a blue-green bacteria that looks black.

It does not look like black algae.

I would try a wide 12 or 18 inch stainless steel pool brush.

Maybe sulfamic acid would work, but that has its own issues.
1631230505437.png
 

JamesW

TFP Expert
Mar 2, 2011
28,291
Does the pool have an ionizer that uses copper and silver?

Has copper or silver algaecide ever been used?

It looks like a copper stain that was caused by calcium hypochlorite that settled on the plaster and caused a black stain that was originally a green copper stain and then maybe someone tried to clear up the black copper stain and made it worse.
 

Shawkr

Member
Sep 9, 2021
22
California
Hi James thanks for the help, I’m relaying all these questions to my mom but since my dad handled the pool maintenance she really doesn’t have answers to your questions. I apologize for that. She also stated, that “although frowned upon, the pools surface is painted because it was the cheapest alternative at the time.” If I grab a stainless steel brush and try to rub the stain, will it remove the ‘painted surface?’
I’m sorry I’m not much help, we really have no pool knowledge and I wanted to help remove the stain before we have a professional come and likely charge a hefty fee!
Thanks again thus far.
 

Enjoying this content?

Support TFP with a donation.

Give Support

JamesW

TFP Expert
Mar 2, 2011
28,291
OK, the paint makes it more difficult to diagnose.

I really can't tell what it is.

For some reason it is local to that particular spot.

I don't know if it can be removed without damaging the paint.

I suspect that it's going to take some sort of mechanical abrasion like a stainless steel brush or underwater sanding discs or maybe sulfamic acid.
 

Shawkr

Member
Sep 9, 2021
22
California
OK, the paint makes it more difficult to diagnose.

I really can't tell what it is.

For some reason it is local to that particular spot.

I don't know if it can be removed without damaging the paint.

I suspect that it's going to take some sort of mechanical abrasion like a stainless steel brush or underwater sanding discs or maybe sulfamic acid.
Understood thank you. I’ll try out your recommendations and report back.
 

Shawkr

Member
Sep 9, 2021
22
California
Hi all, we’ve hired a pool service to come weekly but the guy tells us to ignore it as it’s cosmetic but it’s ugly so that isn’t ideal. I took some water to leslies to test and the results are attached. It appears that the stain is some type of algae as the phosphates level is at 779ppb. I’ve been scrubbing the stain with chlorine tablets and it appears to be helping slightly but isn’t doing as much as I hoped. Are there any other ways to handle a specific stain? I’m trying to avoid pouring chemicals in the pool as our maintenance guy advised not to as he is maintaining the proper levels. Btw, the pool is 17,000 gallons. Please let me know!image.jpg
 

Shawkr

Member
Sep 9, 2021
22
California
I don't think that it is algae.

I would try sulfamic acid.

Be aware that sulfamic acid will convert all FC to CC for months.
So the phosphates level doesn’t mean that it is more likely an algae stain? The iron and copper is 0 so I assumed it’s not metal related.
I assume FC is free chlorine and CC is concentrated chlorine? That means if I put sulfamic acid in the pool I’d need to monitor the chlorine levels? This pool work is hard/confusing! Thank you James!
 

Shawkr

Member
Sep 9, 2021
22
California
So the phosphates level doesn’t mean that it is more likely an algae stain? The iron and copper is 0 so I assumed it’s not metal related.
I assume FC is free chlorine and CC is concentrated chlorine? That means if I put sulfamic acid in the pool I’d need to monitor the chlorine levels? This pool work is hard/confusing! Thank you James!
I should mention. My girlfriend and I scrubbed the stain with a coarse pool brush last night and after we took it out of the water the brush reeked of algae like a dirty turtle tank…
 

JamesW

TFP Expert
Mar 2, 2011
28,291
I really have never seen anything like this spot.

I don't know what it is.

Maybe it's organic or maybe a metal stain or maybe both.

It looks like a black stain covered by a brown stain.

The brown is a weird color that does not match any known algae that is common in pools.

If it was algae, it would not be so stuck on the bottom.

Black algae can be really embedded, but it's really not algae.

Black algae is a type of bacteria called cyanobacteria.

The brown might be a bacteria, mold or fungus, but I really do not know.

I suspect that it will take either very aggressive brushing or maybe sulfamic acid.

You can try a SLAM and vigorous brushing several times a day to see if it will clear up.

The paint will probably be damaged as whatever it is is likely deeply embedded.

If that does not work, I would probably try sulfamic acid.


All FC would become CC.

So you would monitor Total chlorine instead of FC.

1632601881678.png

Overall, the pool is probably due for a full renovation including removal of all old plaster and application of new plaster.
 

Shawkr

Member
Sep 9, 2021
22
California
I really have never seen anything like this spot.

I don't know what it is.

Maybe it's organic or maybe a metal stain or maybe both.

It looks like a black stain covered by a brown stain.

The brown is a weird color that does not match any known algae that is common in pools.

If it was algae, it would not be so stuck on the bottom.

Black algae can be really embedded, but it's really not algae.

Black algae is a type of bacteria called cyanobacteria.

The brown might be a bacteria, mold or fungus, but I really do not know.

I suspect that it will take either very aggressive brushing or maybe sulfamic acid.

You can try a SLAM and vigorous brushing several times a day to see if it will clear up.

The paint will probably be damaged as whatever it is is likely deeply embedded.

If that does not work, I would probably try sulfamic acid.


All FC would become CC.

So you would monitor Total chlorine instead of FC.

View attachment 374146

Overall, the pool is probably due for a full renovation including removal of all old plaster and application of new plaster.
Confirmed, thank you James. We had our third visit with a professional and he said he didn’t know what it was but not too worry about considering my dads passing and my mom likely selling the home in the next year or two. He also said it’s due for a total renovation considering the age and it would cost $15-$20K which my mom does not want to do. In the meantime, ignoring the stain, we are hoping to automate the filter pump as well as the boost pump so that we don’t have to manually do it everyday. We currently have a goldline plus (Hayward) system however it appears to be aging and it isn’t sticking to the set timers. In order to avoid manually turning on and off the filter pump and boost pump daily, he recommended either a cheap fix by installing two simple timers and connecting the two devices to them (~$800 all in) or getting a PSL4 (~$2,500 all in). Do you or anyone else have any input with regards to keeping the filter/boost pump on a daily schedule and which route would be better? Whenever my mom does sell, she will sell it as is (with the pool stain) and let the new owners do with the pool as they please.
thanks.
 

ferretbone

In The Industry
May 24, 2016
166
tx
You have a plaster pool surface not paint.

Get a 6ft piece of pvc pipe, 2 Inch

Push it down in the water over the stain with one end sticking out the water. Slowly pour a bottle of muriatic acid into the pipe so that it falls through the pipe and comes out under water over the stain. I'd pour about 20 ounces at a time. Have a second bottle on stand by.

Pour, wait a minute, move the pipe a little, lift it from the floor a few inches, pour, wait, slowly move and lift repeat.
It should take about 10 mins to empty one bottle. That stain will be gone after two bottles.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Thread Status
Hello , This is an inactive thread. Any new postings here are unlikely to be seen or responded to by other members. You will get much more visibility by Starting A New Thread