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Thread: Blue/Black algae on walls & floor

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    Blue/Black algae on walls & floor

    Hi,
    I bought a house last year that came with a pool. Pool maintenance and shocking consisted of using pucks (trichlor) and Pooltime Shock XtraBlue (dichlor w/ .26% copper) for the past 10 months. Water has been clear, but I started getting blue/black algae forming on the walls & floors. After finding this site and going thru pool school, I ordered the K-2006 test kit knowing my CYA will probably be high.
    CYA=90 FC=17.5 CC=0.5 pH=7.6 TA=130 CH=410


    I wasn't quite ready to change 56% of my water just yet. It's been stormy earlier and figured I'd change the water maybe in April. As a test, I just changed the spa side (400gal). After a week at shock level, the algae is still there. Below are the test results.
    CYA=40 FC=26 CC=0 pH7.6 TA=130 CH=250


    Although the algae is still on the sides and floor, I did notice that the plaster seems a little whiter than the pool side. There was a sale on bleach at Walgreens and I decided to go ahead and shock the pool side even with high CYA. After 3 days, the overnight FC level didn't drop anymore. But the algae is still there. During the day, FC level drops about 4. Note that because of the high chlorine levels, I have to dilute the water 1:3 so as not to use up too much reagents. The FC level could be off by 1.5 I guess. (I'm almost out of #13 and #871 and have ordered some)
    CYA=90 FC=50 CC=0 pH=7.6 TA=130 CH=410


    Questions:
    1) How long does it take to get rid of blue/black algae?
    2) Do I have to keep it at the smaller shock level or higher mustard algae level?
    3) Do I actually have blue algae? See pics attached. There's a pic attached where I left a puck on the floor and it seemed to have lightened the colors of the circular blue-green dotted lines.

    4) Would Polyquat algaecide clear this up?

    5) Should I just replace the water now to get CYA down or change later in April? In one shot 56%?

    6) I initially thought it would be expensive (and wasteful) to change 56% of the water. But realized 9K gallons is 12ccf. That's about the same amount of water we use in 2 months ($35). Didn't realize we actually use so much water on a monthly basis. Anyway, to avoid waste, I though I'd water my lawn and plants with the water. I've read that pool water should be ok. But with high FC (50) levels, I'm not sure if it's ok. Thoughts?

    Shallow end of pool:


    Deep end of pool:


    Puck test for algae:
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by jt-cali
    Hi,
    I bought a house last year that came with a pool. Pool maintenance and shocking consisted of using pucks (trichlor) and Pooltime Shock XtraBlue (dichlor w/ .26% copper) for the past 10 months. Water has been clear, but I started getting blue/black algae forming on the walls & floors. After finding this site and going thru pool school, I ordered the K-2006 test kit knowing my CYA will probably be high.
    CYA=90 FC=17.5 CC=0.5 pH=7.6 TA=130 CH=410

    I wasn't quite ready to change 56% of my water just yet. It's been stormy earlier and figured I'd change the water maybe in April. As a test, I just changed the spa side (400gal). After a week at shock level, the algae is still there. Below are the test results.
    CYA=40 FC=26 CC=0 pH7.6 TA=130 CH=250

    Although the algae is still on the sides and floor, I did notice that the plaster seems a little whiter than the pool side. There was a sale on bleach at Walgreens and I decided to go ahead and shock the pool side even with high CYA. After 3 days, the overnight FC level didn't drop anymore. But the algae is still there. During the day, FC level drops about 4. Note that because of the high chlorine levels, I have to dilute the water 1:3 so as not to use up too much reagents. The FC level could be off by 1.5 I guess. (I'm almost out of #13 and #871 and have ordered some)
    CYA=90 FC=50 CC=0 pH=7.6 TA=130 CH=410

    Questions:
    1) How long does it take to get rid of blue/black algae?

    Welcome to TFP

    I don't know that diagnosing the exact type of algae is going to tell you how long it will take... that's more a function of how much chlorine there is in relation to the CYA and how much exposure it gets to the chlorine. It is more readily dispensed by regular brushing and temperature also plays a part. How cold is the water? The CYA is pretty high. Per the Chlorine / CYA Chart you should have 35 ppm free chlorine or more in the pool all the time.

    For a good overview of this procedure, see Defeating Algae

    Be aware that dilution of pool sample water for testing tends to muliply test imprecision --- so your results become increasingly suspect.


    2) Do I have to keep it at the smaller shock level or higher mustard algae level?
    3) Do I actually have blue algae? See pics attached. There's a pic attached where I left a puck on the floor and it seemed to have lightened the colors of the circular blue-green dotted lines.

    4) Would Polyquat algaecide clear this up?

    5) Should I just replace the water now to get CYA down or change later in April? In one shot 56%?

    6) I initially thought it would be expensive (and wasteful) to change 56% of the water. But realized 9K gallons is 12ccf. That's about the same amount of water we use in 2 months ($35). Didn't realize we actually use so much water on a monthly basis. Anyway, to avoid waste, I though I'd water my lawn and plants with the water. I've read that pool water should be ok. But with high FC (50) levels, I'm not sure if it's ok. Thoughts?

    If this were my pool I would consider draining at least half before commencing a program to kill the algae but it can be done without draining. If you want to drain the water on to plants or grass, let the chlorine level come down to 5 or 10 ppm before doing so.

    Other members will fill in the gaps...

    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
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    Re: Blue/Black algae on walls & floor

    Have you been brushing the pool? Algae on the walls needs to be brushed at least once a day, and preferably more often, while the pool is at shock level.

    Do the algae spots feel slimy? If they feel like the rest of the wall of the pool they might just be organic staining left over from when there was algae. Organic staining will fade slowly as long as you maintain proper FC levels.

    Polyquat is not really effective against an existing algae outbreak. Polyquat is really designed to prevent algae from getting started in the first place. Once you already have algae it doesn't help much at all.

    Lowering CYA would be a great idea.

    Pool water won't harm the lawn at all. There are a few very sensitive plants that react poorly to pool water. If you have any of those you will be aware of it already as they need special attention in any case.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Blue/Black algae on walls & floor

    Knocking out the chlorine is easy with sodium thiosulfate.

    After knocking out the chlorine, sending the discharged water to the sewer, IMHO is best in my area. Your area may be different as some places have salt in the water issues and rules.

    If you are in a relatively high water table area, a few blasts at 25% lowering of the pool may be needed to lower the CYA. Pulling more may cause unwanted buoyancy stresses on plumbing or concrete, liner float, etc...

    Water the lawn really well before discharging on your lawn. This will allow the lawn to fully absorb non-salted water 1st, help to avoid the lawn's roots from absorbing the salt. After discharging, water the lawn again to help dilute any residual salt in the soil.

    Once the CYA is where you want it, chances are good the water will be out of balance. Unless your pH is less than 6.5 or greater than 7.7, shock it hard. Wait 12 hours, brush the walls, check chlorine level, shock again. 12 hours later, vacuum to waste, back wash the filter and balance the water. Keep the filter running until the water balance is where it should be.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

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    Re: Blue/Black algae on walls & floor

    As stated above, if it's a true black algae, brushing is key as it has a tough outer shell that is resistant to chlorine. You have to brush it to expose the insides to the chlorine.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by JasonLion
    Have you been brushing the pool? Algae on the walls needs to be brushed at least once a day, and preferably more often, while the pool is at shock level.
    I brush the pool with a nylon brush. I was only able to find a small s/s brush and only brush a small section of the pool with this 5 times a day. I have not seen a difference.
    Quote Originally Posted by JasonLion
    Do the algae spots feel slimy? If they feel like the rest of the wall of the pool they might just be organic staining left over from when there was algae. Organic staining will fade slowly as long as you maintain proper FC levels.
    They don't feel slimy. But then again, the water is cold and my senses may have been numbed. They don't feel any different when I close my eyes and feel around the area. Also, I've tried pressure washing them with a 1700psi washer and they don't come off. The only test I've done that made a difference is leaving a chlorine puck on the floor.

    Quote Originally Posted by JasonLion
    Polyquat is not really effective against an existing algae outbreak. Polyquat is really designed to prevent algae from getting started in the first place. Once you already have algae it doesn't help much at all.
    OK, I'll skip this test.

    Quote Originally Posted by JasonLion
    Lowering CYA would be a great idea.
    I did lower the CYA to 40 on the spa side with FC=26. It's been a week and the green algae/stains are still there.

    Quote Originally Posted by JasonLion
    Pool water won't harm the lawn at all. There are a few very sensitive plants that react poorly to pool water. If you have any of those you will be aware of it already as they need special attention in any case.
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by PoolGuyNJ
    Knocking out the chlorine is easy with sodium thiosulfate.

    After knocking out the chlorine, sending the discharged water to the sewer, IMHO is best in my area. Your area may be different as some places have salt in the water issues and rules.

    If you are in a relatively high water table area, a few blasts at 25% lowering of the pool may be needed to lower the CYA. Pulling more may cause unwanted buoyancy stresses on plumbing or concrete, liner float, etc...

    Water the lawn really well before discharging on your lawn. This will allow the lawn to fully absorb non-salted water 1st, help to avoid the lawn's roots from absorbing the salt. After discharging, water the lawn again to help dilute any residual salt in the soil.

    Once the CYA is where you want it, chances are good the water will be out of balance. Unless your pH is less than 6.5 or greater than 7.7, shock it hard. Wait 12 hours, brush the walls, check chlorine level, shock again. 12 hours later, vacuum to waste, back wash the filter and balance the water. Keep the filter running until the water balance is where it should be.

    Scott
    My reason for using pool water to water the lawn is to save some water. But it sounds like I might use more water just to pre-soak and rinse .

    I'll have to check with the city requirements on the levels for a sewer dump. I figured the sewer won't mind having extra sanitizer in the system.
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by frustratedpoolmom
    As stated above, if it's a true black algae, brushing is key as it has a tough outer shell that is resistant to chlorine. You have to brush it to expose the insides to the chlorine.
    How long will it take? I've been brushing for a week on the spa side and don't really see a difference between a section that's brushed once a day (w/ nylon brush) and a section that's brushed with a stainless steel brush 5 times a day.
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

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    Re: Blue/Black algae on walls & floor

    Algae would feel slimy (unless your fingers had gone completely numb). The sliminess is normally quite obvious. That suggests to me that the algae is dead and these are either organic stains or metal stains.

    There are various things you can do to explore and confirm the various possibilities. If you have enough test reagent, you can perform an overnight FC loss test to confirm that the algae is really dead. This test can not be done with dilution, as that will introduce too much error in the result. To check for metal stains, try holding a vitamin C tablet against one of the stains for 30 seconds and see if the stain vanishes or changes color.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by JasonLion
    Algae would feel slimy (unless your fingers had gone completely numb). The sliminess is normally quite obvious. That suggests to me that the algae is dead and these are either organic stains or metal stains.
    These have been spreading even when the water was clear. I don't think they are left over stains. If it's algae, it's not dead.

    Quote Originally Posted by JasonLion
    There are various things you can do to explore and confirm the various possibilities. If you have enough test reagent, you can perform an overnight FC loss test to confirm that the algae is really dead. This test can not be done with dilution, as that will introduce too much error in the result. To check for metal stains, try holding a vitamin C tablet against one of the stains for 30 seconds and see if the stain vanishes or changes color.
    I did the overnight loss test on the spa side without dilution. I'm just wondering that maybe the amount of algae on the wall/floor isn't much and the FC they consume isn't above 0.5ppm. FC loss only occurs during the daytime, which I assume to be from the sun.

    For the Vitamin C test, this is what I did. I crushed about 6 500mg tablets inside a baby sock and placed a stone inside to anchor it down. I placed the sock over the puck test I did earlier. The area turned brown after about 30min. After a few hours, it turned white again, but the stains are still there. The picture above for the puck test was taken after the vitamin C test.

    [Edit]
    I went out and rubbed a Vit C table on the stain. The half piece that was left after rubbing I placed on top of the stain for another 30sec. The stains didn't change at all.
    I was actually expecting the area to turn a little brown as in my previous sock test. But it didn't occur. Any ideas why there's a difference?
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

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    Re: Blue/Black algae on walls & floor

    Right now it sounds like copper stains. Copper stains can remain unchanged, or get either lighter or darker, when doing a vitamin C test. Copper stains are often blue/green. Copper stains can usually be lightened with acid, which matches with the lighter area where you had the trichlor puck (trichlor is fairly acidic, in addition to containing chlorine). If there is a plausible source of copper in the water then copper is the leading possibility. Copper can come from using a copper based algaecide or from having a heater with a copper heat exchanger and having had the PH low for a while.

    Algae that is still alive seems extremely unlikely. Algae does not grow and spread while you are at shock level. Algae, even black algae and mustard algae, will either die completely, or worst case, appear to vanish and then reappear when the FC level gets lower. If all of those stains were living algae they would be using up a substantial amount of chlorine, and they would vanish, or at least fade dramatically by the time the overnight FC loss test showed a loss of 0.5 or less. Also, algae is slimy.

    The vitamin C test rules out iron stains. Iron stains would vanish, or at least lighten significantly, when you did the vitamin C test.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by JasonLion
    Right now it sounds like copper stains. Copper stains can remain unchanged, or get either lighter or darker, when doing a vitamin C test. Copper stains are often blue/green. Copper stains can usually be lightened with acid, which matches with the lighter area where you had the trichlor puck (trichlor is fairly acidic, in addition to containing chlorine). If there is a plausible source of copper in the water then copper is the leading possibility. Copper can come from using a copper based algaecide or from having a heater with a copper heat exchanger and having had the PH low for a while.
    I used shock that has copper algaecide. I guess I was making the problem worst everytime I tried to remove the stain by shocking it.

    How do I determine for sure that it's copper stains? And if it is, use ProTeam's Metal Magic to remove them?
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

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    Re: Blue/Black algae on walls & floor

    I'm wondering if you perhaps have both problems? (thinking out loud here.)

    You did state the puck lightened the one spot significantly (shown in the picture above) which indicates organic. Try using a stainless steel brush, since the surface is plaster, while the chlorine is up I don't know that the nylon would be effective enough. You stated the spa seemed lighter (of course this could be optical illusion or something...)

    I wonder if you do have some restistant algae issue, and then copper stains as a result of algaecide use?

    Copper staining can be a problem, if it's indeed copper...
    Helpful links: Pool School; CYA/Chlorine Chart
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    Re: Blue/Black algae on walls & floor

    Morning!

    Have you tested for copper? I would be interested to know the result of the test.
    I doubt you have algae and copper, copper is too effective as an algaecide. Never use these copper based products in your plaster pools and worst of all, the more you brush the surface the more fresh plaster with a high PH (8.3 or higher) you will expose (not the pH of the bulk pool water) but right on the surface so that is likely to cause more copper (if it is copper) to drop out of suspension and stain at the bits you have just cleaned.

    IMO test first, sequester if it is copper then begin to brush but you may need to drain and acid clean.

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    Re: Blue/Black algae on walls & floor

    Well I was thinking to suggest to test for copper, but if it's already deposited in the surface it won't necessarily show up in the water tests. I am also wondering if it's just organic staining left over from algae and not necessarily live?

    How recently was the application of algaecide applied?

    (it certainly can't hurt to test for copper, I agree with teapot might as well go ahead and check.)
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by jt-cali
    My reason for using pool water to water the lawn is to save some water. But it sounds like I might use more water just to pre-soak and rinse .

    I'll have to check with the city requirements on the levels for a sewer dump. I figured the sewer won't mind having extra sanitizer in the system.
    When I was looking at a big drain about a year ago, I found a brochure by the Santa Clara Valley Urban Runoff Prevention Program with a variety of info, including this phone number: Sunnyvale Water Pollution Control Plant, (408) 730-7270.

    I think in this case, watering the lawn is not a good idea--not so much because it will hurt the lawn but to keep stuff out of the ecosystem. The rules are that you drain into the sewer, not onto the ground.
    --paulr
    BBB "Intermediate Swimmer"
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  17. Back To Top    #17

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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by teapot
    Morning!

    Have you tested for copper? I would be interested to know the result of the test.
    I doubt you have algae and copper, copper is too effective as an algaecide. Never use these copper based products in your plaster pools and worst of all, the more you brush the surface the more fresh plaster with a high PH (8.3 or higher) you will expose (not the pH of the bulk pool water) but right on the surface so that is likely to cause more copper (if it is copper) to drop out of suspension and stain at the bits you have just cleaned.

    IMO test first, sequester if it is copper then begin to brush but you may need to drain and acid clean.
    I haven't tested for copper. I went down to Leslie's to check if they have anything I can use to test if the staining is copper, but they had none. They used to have a stain id kit (I'm assuming Jack's). They gave me a water bottle to bring some water in for testing.

    Are there any recommended test kits available for copper?
    Does FC level affect copper testing? Should I wait for the FC level to drop before taking a sample in to Leslies's?
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

  18. Back To Top    #18

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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by frustratedpoolmom
    Well I was thinking to suggest to test for copper, but if it's already deposited in the surface it won't necessarily show up in the water tests. I am also wondering if it's just organic staining left over from algae and not necessarily live?

    How recently was the application of algaecide applied?

    (it certainly can't hurt to test for copper, I agree with teapot might as well go ahead and check.)
    I'd think there would still be copper in the water even when stains are present. And I thought I read somewhere that staining would occur only after a threshold is exceeded (0.3ppm?). I'm pretty sure I have copper in the water as I've shocked w/ algaecide. If my tests come back with copper levels below 0.3ppm, would that mean the stains aren't copper?

    I applied Pooltime Shock XtraBlue(<--copper) monthly from May09-Jan10. I actually applied it twice in Jan. Then I found this site, read the labels and stopped.
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

  19. Back To Top    #19

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    Re: Blue/Black algae on walls & floor

    Quote Originally Posted by PaulR
    Quote Originally Posted by jt-cali
    My reason for using pool water to water the lawn is to save some water. But it sounds like I might use more water just to pre-soak and rinse .

    I'll have to check with the city requirements on the levels for a sewer dump. I figured the sewer won't mind having extra sanitizer in the system.
    When I was looking at a big drain about a year ago, I found a brochure by the Santa Clara Valley Urban Runoff Prevention Program with a variety of info, including this phone number: Sunnyvale Water Pollution Control Plant, (408) 730-7270.

    I think in this case, watering the lawn is not a good idea--not so much because it will hurt the lawn but to keep stuff out of the ecosystem. The rules are that you drain into the sewer, not onto the ground.
    --paulr
    Thanks for the number Paul. The Sunnyvale website says to drain to sewer and listed the same number. I called them to check on watering the lawn and they just said it's ok if chlorine is 0 so as not to harm the grass.
    21,000 gal oval pool; Pentair IntelliFlo VS-3050 pump; Purex SM-2060 DE filter; Polaris 280 cleaner; Purex Tropic Isle C360 heater;

  20. Back To Top    #20
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    Re: Blue/Black algae on walls & floor

    The chlorine doesn't matter, it won't have any effect on the grass. Salt can be an issue in extremely arid areas where it might build up over time, most places salt isn't a problem at all as it will wash away when it rains.
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