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Thread: Small Black Spots - Pictures

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    Small Black Spots - Pictures

    Hi,

    Just want to thank everyone in advance!

    New to this site, however, I have been reading a lot on here in the last few years! Here is my question....

    Does anyone know what these spots are? My pool was recently plastered (about a month ago) and these showed up (or I just happened to notice them) about 4-5 days ago. They are only in the shallow end. Tried brushing them with a nylon brush (since the plaster is still curing) and they aren't moving/vanishing. I tried to scrape one off (they are tiny) with my nail but nothing happened.

    After reading, I'm thinking black algae but I don't want to jump the gun and do something that will ruin the plaster!

    I've pretty much maintained the pool chemicals, however, the first two weeks, I did not use stabilizer or chlorine since I was told by the pool co. to wait two weeks. Of course, the temp here was ridiculously high! I have been adding algaecide and metal out since week 2. When I initially started using the pucks, they were gone within a day until the stabilizer was added.

    Here are my recent numbers:

    TC: 1.37
    FC: 0.73
    CC: 0.64
    PH: 7.8 (added acid yesterday)
    Hardness: 227
    Alk: 92
    CA: 71
    Iron: 0
    Copper: 0

    Pool is approx. 25k Gallons, Gunite, White Plaster.

    The pool store gave me great suggestions if it is black algae, however, I did not have a picture to show them.

    Any help would be great!
    Attached Images Attached Images

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    Mod Squad Bama Rambler's Avatar
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    Re: Small Black Spots - Pictures

    If you can't scrape it off it's most likely a stain of some sort. I'd call the plasterer and let them look at it. There are ways of determining what they are but I wouldn't do anything till the plaster folks have a say about it.
    Dave J. TFP Moderator
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    Mod Squad jblizzle's Avatar
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    Re: Small Black Spots - Pictures

    Welcome to TFP!!!

    You seem to be getting some horrible advice. There should not be a problem adding CYA and chlorine to your pool ... you have to or it will turn into a swamp. Also realize that there is NO reason to have to add algaecide if you keep the appropriate FC levels for your CYA level.

    Are those test results from a pool store? IF so, stop trusting them and order yourself a good test kit (see the link in my signature for the recommended ones). For example, if you have not added stabilizer (CYA), except for what is in a few pucks, there is no way your CYA is 71ppm as their results show.

    IF (and that is a big if since you did not do the test yourself), your CYA is 70 ppm , then you should NEVER be letting your FC below 5ppm ... see the chart in Pool School.

    Also, I would not trust anything the pool store said about the "black algae" until you confirm their advice here ... what were their recommendations?

    You should start reading through Pool School (button at upper right of the page) a few times to start to understand your pool's chemistry.

    Regarding the black algae ... if it is it should scrap off with your fingernail and look dark green on your hands.
    Jason, TFP Moderator
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    Re: Small Black Spots - Pictures

    I know these spots weren't there at least the first 2.5 weeks. This is the 3rd plaster job we have had since the pool was built 3 years ago so...you can see where we stand with the pool company that built it (NON recommend). The reason I know is we went over the plaster job with a fine tooth comb.

    At first I thought maybe it was from fireworks we had on the 4th but, again, it doesnt brush away. I will have to go try to scrape it off again. I cant remember if I brushed prior to trying the first time since..I have to brush so much the first month!

    I was hoping the spots looked familiar to someone...or there is something I could do to check before treating! Hopefully the pictures are clear enough. I think the last picture you can enlarge.

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    Mod Squad jblizzle's Avatar
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    Re: Small Black Spots - Pictures

    Well, now that you do mention fireworks (which are made up of metals) ... if some of the small pieces fell into the pool, it very well could be metal stains. To confirm, you can try rubbing them with a vitamin C tablet.

    Although I still stand by everything I wrote before.
    Jason, TFP Moderator
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    Re: Small Black Spots - Pictures

    Jason,

    I was told week 1 and 2 no chlorine (by the pool builder). I added both stabilizer and chlorine tabs the beginning of week 4. I have shocked twice since the beginning of week 3 (Friday will be 1 month).

    The results were from the pool store. They said there is defiantly something going on in the pool since the chlorine numbers were so off. They suggested treating it with shock and algaecide (for blk algae). There is strict regimen to follow treating for black algae. I have no problem doing that, however, since its new plaster, I'm a little gun shy!

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    Mod Squad Bama Rambler's Avatar
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    Re: Small Black Spots - Pictures

    It's always smart to follow the installers recommendations on new installs no matter how wrong they seem. They have the say on the warranty and if you fail to follow their instructions they can use that to deny warranty. I don't disagree with JB but reality gets in the way of right in these cases. That's why I said to contact the plaster guy before doing anything they could construe as voiding the warranty.
    Dave J. TFP Moderator
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    Mod Squad jblizzle's Avatar
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    Re: Small Black Spots - Pictures

    I have never heard of not adding chlorine for 2 weeks that is silly, but you need to follow their advice to maintain warranty. Personally I would have asked for their reasons for the recommendations. Here is an article in Pool School about how to start a pool:
    pool-school/pool_plaster_start-up

    What you have done is not what we call "shocking" it is a verb here ... see Pool School ... a process to hold the FC at elevated levels. Blindly throwing in powders is not going to help and is going to cost you more $ than needed.

    What is their "strict regimen"? I guarantee you could save yourself $ by learning here and letting us help you ... instead of trusting a pool store who is in business to make money.
    Jason, TFP Moderator
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    Re: Small Black Spots - Pictures

    Ill take a look at the test kits. I had one with my old pool and it just stressed me out!

    The fireworks we had were pretty big (mortars). They weren't shot off near the pool but, they were very large! The only reason I thought maybe it was that is because its in the shallow end only. Ill try the vitamin C tab. Is that alright to use on fresh"ish" plaster?

    And how do I get my FC higher? Or to get all the chlorine numbers on track for that matter!!! Ill also check the pool school out as well. Im more of a "cliff notes" kinda girl so, sometimes too much info at once hurts !

    Thanks for the quick responses!

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    Mod Squad jblizzle's Avatar
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    Re: Small Black Spots - Pictures

    As Bama said, you may want to consider talking to the plaster guys ... although testing with a tablet in one spot should not hurt anything.

    Since your CYA appears high already, you need to stick to liquid chlorine or bleach (yup just plain old 6% bleach) to maintain at least 5ppm FC.

    The key to the kit is the FAS-DPD chlorine test ... it is easy, you just count drops until the water turns clear (no color matching). It really will be the best investment you can make to maintain your pool (and save $ by not trusting, or even going to, the pool store).
    Jason, TFP Moderator
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    Re: Small Black Spots - Pictures

    Correctly identify your problem first. Black algae will scrape off partially with your fingernail, it will be slimy and should be greenish/blackish when you scrape it off.

    If it doesn't display those characteristics, it's not black algae.

    Post back your findings.
    Dave S.
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    Re: Small Black Spots - Pictures

    You both are right about the warranty. You have no idea.

    The store wants me to treat for blk algae. Brush the pool as well as thoroughly brush the black spots...back flush if necessary. Add shock to the pool (dichlor) 2x what I normally use for my pool size. Wait 15 mins. Add silver algeacide at a rate of 8 oz every 10 mins thru the skimmer until I reach the recommended dose. Let the pool run continuous for 72 hours, however, after 48, back flush. Follow up w/metal out a few days later then use the blk algaecide twice (1 week from initial and then a week later), however, with the normal amt of shock. After that, normal algaecide.

    I had a pool at my old house which was over 20 yrs old and never had an issue!

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    Mod Squad Bama Rambler's Avatar
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    Re: Small Black Spots - Pictures

    I really don't believe it's algae. As you've already stated, you can't scratch it off. Algae you could definitely scratch off.
    Dave J. TFP Moderator
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    Mod Squad jblizzle's Avatar
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    Re: Small Black Spots - Pictures

    You MUST NOT use dichlor anymore ... your CYA already appears to be too high (the pool store will disagree with this as they "allow" much higher levels than are realistically workable).

    Algaecide is a waste of money. All you need is the correct FC levels.

    They can not tell you when you should backwash. That is a function of your pool, pump, plumbing and filter size. You should be cleaning the filter when the pressure goes up 20-25% of the clean pressure.

    Do you have metals in your pool to justify the use of metal out?

    I don't like anything the pool store has told you, but that is just me

    ... and as Bama just stated again, you have not even confirmed it is algae.
    Jason, TFP Moderator
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    Re: Small Black Spots - Pictures

    Quote Originally Posted by YZFR1Girl
    Ill take a look at the test kits. I had one with my old pool and it just stressed me out!
    Take a number of read through's at Pool School, and then read them again. You were stressed because you didn't have the information and tools to use the results of testing properly. Also, very likely you had an inefficient and ineffective test kit. Do take the recommendations here for a proper test kit to heart. I assure you that no one here feels stressed by their kit, but rather the opposite. Armed with knowledge and the wealth of assistance available here, your kit will actually de-stress you.

    And how do I get my FC higher? Or to get all the chlorine numbers on track for that matter!!! Ill also check the pool school out as well. Im more of a "cliff notes" kinda girl so, sometimes too much info at once hurts !

    Thanks for the quick responses!
    You need to add chlorine to raise the level. Not pucks, they'll continue to add CYA to your pool. Liquid chlorine (bleach) is what you'll want to use from now on. Pool school will teach you how to use it, and if you have questions about what you're reading there, just ask here. Pool school is absolutely cliff notes style, it's the forum that's got all the nitty gritty non-cliff notes information (use search at the bottom left of any page to read the good nitty gritty threads).

    I'd still talk to the plaster people about these spots. Have they seen them yet?
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Re: Small Black Spots - Pictures

    Thanks for all the responses (now Im confused though )

    I though the dichlor was good for new plaster UGH! Now I have no idea how to administer chlorine etc other than throwing tabs in the skimmer!!

    I use the metal out because we have well water and when I top off the pool, we use the hose....our water is VERY high in Iron! I use the algaecide because we have a LOT of trees..I mean acres so, something is bound to end up in the pool plus, we go to the river to jet ski...I know..rinse or change before going in the pool right??!

    I do have to read up...Ive never used just bleach in my pool (either one) just the liquid at the pool store...probably the same stuff just more money!

    ll also look into that test kit...sounds simple enough. My old one what a train wreck...I ended up throwing it in the trash I would get so mad!

    Oh, and the plaster people, no one spoke English.....

    Ill scrape and try the vit C. I will post an update !

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    Mod Squad jblizzle's Avatar
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    Re: Small Black Spots - Pictures

    Now to confuse you more ... DO NOT put pucks in the skimmer:
    1. it is bad for the equipment if the pump is not on 24/7
    2. The pucks are trichlor and also add more CYA

    The liquid chlorine you get from the pool store is 10% or 12.5% strength ... the bleach is 6% ... same stuff. Usually the bleach is cheaper per the amount of FC added, but sometimes the stronger stuff is cheaper.

    Again, the algaecide is not needed IF you keep the FC in the correct range.
    Given the well, water, you may need to keep use a sequestrant, review: pool-school/metal%20stains There are some that we recommend that work better ... I am not sure what is in the Metal Out you have been using.

    Order a kit. Read Pool School a few times. You will be happy you did.
    Jason, TFP Moderator
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  18. Back To Top    #18

    Re: Small Black Spots - Pictures

    Thanks again and I will read and prob get my own kit. The sequesterant I was using was Ketrol. They suggested I start with Jacks Magic Magenta since there are phosphates around here (farms).

    I do need to get the chlorine stuff in check. I have little ones who I dont want to get sick!

    Gonna try the vit C tab tonite...I HOPE that works! I dont really want to put all that **** in my pool if i dont have to!

  19. Back To Top    #19
    Mod Squad jblizzle's Avatar
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    Re: Small Black Spots - Pictures

    AH the next pool store buzz word!!!

    Ignore Phosphates ... they are algae food, but if you keep the FC at the correct levels, the algae can not grow anyway. Just another product for the pool store to make money on.

    Do you see yet how the key to a clear pool is the correct chlorine level given your CYA level?
    Jason, TFP Moderator
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  20. Back To Top    #20

    Re: Small Black Spots - Pictures

    Yep...gotcha. Its just a matter of me getting the two in check. Ill read up on how. Old habits are hard to change so...I have to make sure I understand this "new to me" method! Thanks~!

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