Black Algae, maybe? It's getting worse.

[ralphsyv]

We just got back after 4 months and the black algae (or whatever this is) is getting worse. We had a pool service we fired almost a year ago. They were mostly the cause of this and some other problems. The manager said we had black algae, but didn't have a solution that worked.

The new service attempted to get rid of the black algae with no success. They said the previous service damaged the pebbletec surface with acid and exposed some bare concrete underneath. So, that's where this is happening.

I've been trying to brush it, but i'm not going to be able to get rid of it brushing/algaecide. Will acid washing get rid of it? There's a lot of staining otherwise, so I'd like to clean off the staining, but I'm just concerned about doing more damage to the surface.

 

[ajw22]

There are many threads about suspected black algae. Here is a recent one…

Getting rid of Phosphates cured my 5yr standoff with black algae

Wanted to share I documented my issue here: https://www.troublefreepool.com/threads/very-sad-return-of-black-algae-after-slam.161684/ Small specs of black algae on the plaster and grout. Pool had been SLAMMED to 100ppm for 20 days, FC kept elevated etc. Pool always passed the OCLT and CC always...

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Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.

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[ralphsyv]

Thanks, Allen. Any idea if reducing phosphates really makes a difference? I know black algae is resistant to chlorine. There's probably a lot of built up residue on the pebbletec surface that is feeding the black algae. That's why I think maybe acid wash will be needed to clean the surface and get rid of black algae.

 

[JamesW]

Black algae is a type of bacteria.

It is like a mold that you can scrape off.

Scrape some from a spot.

If it is not soft and mushy, it is not black algae.

If it isn't black algae, I suspect that it is copper stains.

For bad copper, I would suggest a sulfamic acid product like Jack's #2 copper and scale stuff and then a drain and refill if you can drain safely.

Pools can pop out of the ground if drained during a high water table.

Consult a local expert before draining.

 

[JamesW]

What is this? Black algae or something else?

The pool service said it is black algae. Looking closer it looks like some white or silver spots surrounded with something black - basically cheerio size black circles. Some of the Paramount cleaning nozzles have a lot of algae? and black junk or mineral staining? It's hard to get a good photo.

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Thanks for your help! I think the silver from the Nature2 cartridge has deteriorated and small nuggets of silver are escaping through the cartridge and they end up on the bottom of the pool and causing the black stains.

 

[ajw22]

Thanks, Allen. Any idea if reducing phosphates really makes a difference?

Depends what your phosphate level is. You have a number?

Phosphates is algae food. So getting rid of it may help but is not a cure all. It still takes intensive chlorine to kill it.

I know black algae is resistant to chlorine. There's probably a lot of built up residue on the pebbletec surface that is feeding the black algae. That's why I think maybe acid wash will be needed to clean the surface and get rid of black algae.

An acid wash can also etch your plaster and loosen pebbles. Folks have had their pebble finish ruined by over aggressive acid washing.

 

[JamesW]

The brown is silver, the turquoise is copper, the black is also probably copper that has been oxidizer further than the turquoise copper.

 

[ralphsyv]

Black algae is a type of bacteria.

It is like a mold that you can scrape off.

Scrape some from a spot.

If it is not soft and mushy, it is not black algae.

If it isn't black algae, I suspect that it is copper stains.

For bad copper, I would suggest a sulfamic acid product like Jack's #2 copper and scale stuff and then a drain and refill if you can drain safely.

Pools can pop out of the ground if drained during a high water table.

Consult a local expert before draining.

Thanks, James! It's definitely not soft/mushy. It does not scrape or brush off. I'm suspecting it might be a lot of copper and silver build up? There was a Nature 2 system for years that added a lot of copper and silver. And the first pool service added more silver. I don't know what the new service added, so I'll check with them.

 

[ralphsyv]

Depends what your phosphate level is. You have a number?

Phosphates is algae food. So getting rid of it may help but is not a cure all. It still takes intensive chlorine to kill it.



An acid wash can also etch your plaster and loosen pebbles. Folks have had their pebble finish ruined by over aggressive acid washing.

I don't think I have a way to test phosphate level. I have Taylor 2006C, I don't think there is a phosphate test.

 

[ajw22]

I don't think I have a way to test phosphate level. I have Taylor 2006C, I don't think there is a phosphate test.

It doesn't. A pool store would test it for you or Taylor has the K-1106 phosphate test kit. The Taylor K-1106 test kit can test at phosphate levels of 0-1000 ppm or 0-6000 ppm. It has two different color comparator cards for the two tests.

 

[JamesW]

I suspect that the black is probably copper and not black algae.

I suspect that a sulfamic acid treatment would be the most likely fix followed by a drain and refill.

Florida is notorious for floated pools due to the water table.

Are you near a body of water?

If yes, what is the pool elevation relative to the surface of the body of water?

Do not drain without confirming it is safe to do so.

 

[JamesW]

Turquoise copper stains can turn black when someone throws calcium hypochlorite in the water and some hits the floor and oxidizes the copper to a more oxidized state.

Sometimes people will drop calcium hypochlorite on black algae to try to clear it up.

That might have happened here, but it just made the black worse because it was copper and not black algae.

 

[JamesW]

In my opinion, this brown is definitely silver stains and the surrounding turquoise is probably copper.

 

[ralphsyv]

The brown is silver, the turquoise is copper, the black is also probably copper that has been oxidizer further than the turquoise copper.


View attachment 360602

I suspect that the black is probably copper and not black algae.

I suspect that a sulfamic acid treatment would be the most likely fix followed by a drain and refill.

Florida is notorious for floated pools due to the water table.

Are you near a body of water?

If yes, what is the pool elevation relative to the surface of the body of water?

Do not drain without confirming it is safe to do so.

There's a canal behind the fence. Maybe 30 feet away and 10 feet lower. It depends on amount of rain. The pool is about 7 feet deep.

 

[JamesW]

I would probably try sulfamic and then a drain and refill.

Consult with a local professional before draining and refilling so you don't float your pool.

 

[ralphsyv]

Yeah, I'm definitely going to have to check in with a local professional. It's raining about 2-3 inches every day.

 

[ralphsyv]

It seems like there's a high level of copper/silver/metals in the pool. I'm trying to fix the pool light and everything stainless steel is coated with a thick layer of black crusty stuff. Everything pvc is stained brown and has white crystals on the surface.

 

[ajw22]

Could be a combination of metals and scale.

Wipe it down with a slurry of vitamin C and see what comes up.

Stains in Your Pool

The stained pool is beyond embarrassing. Our in-depth Guide to remove stains in your pool will help you to remove the stains and prevent them in the future.

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