Algae keeps coming back after SLAM

djdonte

Well-known member
Mar 25, 2019
138
Houston, TX
I’ve tried SLAMMING twice now and both times the water looks beautiful, and I pass a OCLT after two days or so, However maybe a week or so later the algae creeps back, on rougher spots on my plaster. I know I need a replaster, just isn’t in the budget right now. The areas the algae seem to be “embedded” in the plaster, only a stainless brush will remove it. The standard brush does nothing. I am not sure what to do and am worried about further damaging the surface with repeated stainless brushing. I removed the light niche, found a tiny bit of algae, and a good amount hidden near the skimmer last slam. What I can’t keep from coming back is in the pictures. You have to look close to tell between rough textured plaster and green.

Last tests were 8 FC, 0.5 CC, 60 CYA. I have been adding about 2-2.5 worth of bleach FC each night to account to sun light and leave me back at 7-8 FC. Running pump 8 hours a day.
 

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mknauss

Mod Squad
TFP Expert
May 3, 2014
15,254
Laughlin, NV
Once you pass the three criteria for the successful SLAM, maintain your minimum FC at 20% of CYA for a couple weeks and see if that helps defeat the algae.
 
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cfherrman

TFP Guide
May 10, 2017
2,199
Hays, Kansas
Things to consider

Getting a robot, they clean very well and get crud you can't see off the floor, I'm not sure the spot you are referring to a robot can reach.

Definitely do the 20% cya treatment, you might just have to run more FC till you find the culprit.

Treat your plaster with a 0 ta treatment to attempt to soften up the plaster, it's like a acid wash but much much softer. Do some searching if this interests you.

If everything has failed and there is nothing else to do and your sure you doing everything right and don't want to replaster. Test for phosphates and treat them.
 

djdonte

Well-known member
Mar 25, 2019
138
Houston, TX
I have some PhosFree left over from my days of being "pool stored." It worked but clogged my filters quickly. Any way to test for phosphates without dealing with leslies? I have the suction pool cleaner, so not really interested in getting a robot, but no cleaner will get under the light niche or in the skimmer.

Also any concerns on using the stainless brush repeatedly? Seems to be the only thing that gets the green out of the rough patches.

I am not familiar with 0 TA treatment so I will have to check it out. TA, CH, and CSI all look pretty good. Cant say the same for whoever owned the home before.

I am planning to SLAM here soon and leave it at SLAM for another day or two after I pass, then leave the FC at about 12 for a while. The pool was obviously not taken care of by the previous homeowner and I have been dealing with it ever since.
 

cfherrman

TFP Guide
May 10, 2017
2,199
Hays, Kansas
You probably have phosfree with clarifiers, check the bottle. Taylor sells a phosphate test. This is close to a last resort kind of thing.

Idk on the brush, I would say it can lt make your plaster smoother as it's like using sandpaper on it.

Typically a 0 ta treatment is to get rid of calcium scale as it makes the water super aggressive.
 

djdonte

Well-known member
Mar 25, 2019
138
Houston, TX
I started my SLAM and brushed my pool, as well the areas I found hidden algae last time (none this time). My theory is the weathered rough plaster is creating a ton of surface area for the algae to grow/hide, as well as being harder to clean. The reason I say this is there was only a slight shade of green in these areas, but when I hit them with the stainless brush a ton of green dust came off and my pool got extremely cloudy. There is a few spots where my plaster meets the waterfall rock that is very tough to clean. Perhaps I stopped my SLAM too early last time. I am going to leave it for a few solid days after I think I'm done, then clean the filters and keep the FC at 20 percent CYA.
 

djdonte

Well-known member
Mar 25, 2019
138
Houston, TX
Will do. Another problem I am seeing is the plaster under the waterfall rocks is near impossible to get with a standard brush. I need a brush kind of like a toilet brush. Not even sure if such a thing exists for a pool.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
DJ, definitely continue with the SLAM. You should never see green like that, and by now I'm sure you know that. It's just frustrating. But I want to clarify something noted earlier - your plaster. In post #1 you first note the rough plaster and that it needs to be re-done. But later there was talk about a zero TA treatment. So if the plaster is pitting because of age or poor care in the past, you probably don't want to do a zero TA treatment as that makes the water aggressive for a while, and it doesn't sound like you need that with your current plaster. But if the roughness is built-up calcium scale, that's a different story.

Back to the algae, it's good you found places it's been hiding. So besides the waterfall and light, no other places for algae to hide correct? I know there are other "creative" scrub brushes out there for your waterfall. Might have to just Google a bit. One of the downfalls to a decorative feature I suppose, but you can get it. As noted, even if you pass the SLAM criteria this weekend, you might consider keeping the FC slightly more elevated for another week or so. Best to do it now before our TX sun really starts to crank-up. Best of luck! :swim:
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
There you go! Hopefully that will help. Oh, I forgot to mention something else - the Phosphate remover you might have left over. If you elect to use some later, that's certainly up to you. But I wouldn't add any of it at this time since the elevated FC will probably just oxidize it anyways. Once you pass the 3 SLAM criteria, and perhaps leave your FC elevated for another week or so for the organic staining and any residual material that may be embedded, you'll eventually let the FC fall back to TFP normal standards. That would be the time to use a little of that IF you want to. No guarantee it will have an effect on what you've been dealing with, but adding it now would probably just be a waste.
 

djdonte

Well-known member
Mar 25, 2019
138
Houston, TX
Yes I am now. Honestly I think my CYA is closer to 50 though. Maintaining just under 30 FC to account for UV loss. Those numbers you quoted were my normal readings after stopping SLAM. I thought keeping the FC on the higher side of the range for my CYA would prevent this.
 
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setsailsoon

LifeTime Supporter
TFP Guide
Oct 25, 2015
1,131
Stuart/FL
DJ,

I had a similar problem early after I started TFP. Never got to a green pool but did get some areas with light green patches like yours. When FC levels were border-line too low I'd get algae start to grow in the same areas that looked just like yours. So I got my scuba gear on and looked closely and found tiny little spots that I thought from the surface were part of the pebbles in the plaster. They were actually almost black but as I rubbed them the surface layer came off and revealed green and light-green classic algae color. These were the same areas that I had the patches form in. I did two things to resolve this. First I went to SLAM level on the FC while scrubbing daily. Second, I re-directed the return jets in an attempt to improve flow. I continued SLAM a few days after passing the OCLT test while scrubbing these areas. My theory was that the algae were forming some kind of dead layer on the outside that protected the cells inside. Then when conditions got favorable the live cells would cause a mini, and local bloom in these areas. No idea if my theory is right but the actions worked. No return of this problem since - probably partly because this made me more diligent about monitoring my FC.

Chris
 
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djdonte

Well-known member
Mar 25, 2019
138
Houston, TX
Thanks chris. I’ve looked everywhere and the only place I can find active algae is under my rocks so I ordered that brush. I check my FC at least twice a day so I know I never went below min or even close. Plan to brush the pool really well twice a day while slamming, hold the slam past when I meet the 3 passing criteria then leave FC at 20 percent of my CYA for a while to see if that cures it.
 
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splashpad

Bronze Supporter
Aug 2, 2017
1,979
SE Kansas!
Yes I am now. Honestly I think my CYA is closer to 50 though. Maintaining just under 30 FC to account for UV loss. Those numbers you quoted were my normal readings after stopping SLAM. I thought keeping the FC on the higher side of the range for my CYA would prevent this.
It will if
1) the CYA reading is accurate
2) with no active algae growth :)
3) It's maintained at that level daily
4) Some like to preventively 'bump' FC, after a big swim day/party or after a 'weather' event
 

djdonte

Well-known member
Mar 25, 2019
138
Houston, TX
What’s the best technique on the black dot test? Honestly sometimes I think it disappears at 35 and sometimes I think it’s 50. I even invested in the blue devil test and still having trouble grasping it.
 

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