Why Does My Pool Keep Getting Algae?

17 thoughts on “Why Does My Pool Keep Getting Algae?

    1. The thing about phosphates is that it is food for algae, but it does not create algae. So as long as your pool is properly dosed with chlorine, the algae can’t bloom to then eat the phosphates present in the water.

  1. Hi,

    While I have removed the algae in the water, I am interested in knowing how to remove the black deposits (that look like scrapes) and have taken hold in random spots within pool walls. Is there anything useful to address this issue?

    On the algae video, one question I do have is; what exactly should a pool be treated with routinely — besides chlorine. I tend to shock my pool once a week (as instructed to do so) but feel I need to be more precise with how I’m running the maintenance operation. Can you provide some tips in this area as well?


  2. I’m fighting mustard algae. I’ve had it since I first had my pool put in five years ago, but I just thought it was little specks of dirt. For three summers I have tried to get rid of it. I’ve already triple shocked my pool 8+ times in the last two weeks. I’ve used 10 lbs of Yellow Out or Yellow Klear. I’m spending so much money triple shocking and it just comes back. I don’t know what to do.

    I have a saltwater fiberglass pool approximately 15,000 gallons.

    1. I dont work for Inyopools. Just knowledgeable about pools.
      1. First I would treat your water to knock down the algae while making sure chlorine and PH is good.
      2. Take water to a pool store have them check your water for phosphates. Algae uses phosphates for food. I believe you want your phosphates lower than 250 ppm. You will want to use a “no phosphate treatment”. No phosphates then your algae should be minimal. follow instructions on chemical bottle and or pool store.
      3. What other chlorine do you use when your pump is not running your salt system? Salt system only makes chlorine when your system is running.

  3. I took a Water Sample to the local Pool Store,when I bought some Algycide.They tested the Water and mentioned that it had to much Acid.Solution ,drain your Pool Water and put fresh water in .Bring new water sample to Store.Answer;with the new Water ,I don’t need a test. Question about the Acid. Do I have to much Muriatic Acid in the Water or do I need more ? PH seems to be fine with my Home base test ?

    1. Ok, if your PH is fine then the pool store was referring to cyanuric acid. Its a byproduct of chlorine it’s the double edged sword effect. You want your cyanuric acid level below i believe 50ppm. There are some cyanuric acid removers out on the market I haven’t used them so I can’t attest to their effectiveness but I’ve heard they do work. The removing of water sometimes half or a complete drain and refill removes it also. I use regular liquid bleach it’s chlorine and works great for me.

  4. Should you always shock after rain? Also, if you brush the sides of the pool, doesn’t that spread the algae?

    1. No, algae anchors itself to pool sides and floor. The idea is to treat first following directions of chemical or pool supply house. Then brush the sides and floor to get the algae into the filter then backwash or clean you filter media to remove the dead algae

      1. You are right on with your article but like someone said earlier…if you remove the food, phosphates, they wont bloom as often or as prolific. I have dealt with algaes and it has always started getting better with chlorine and brushing but if it gets treated and brushed 1 time anweek, it is back when that 1 times come back around. Removing the phosphates minimizes the reoccurrence and helps you conquer the bloom. Yellow and black are different stories.

        1. Do you only add chlorine to your pool once a week? If that is the case, it sounds like you would need to do a booster shot of chlorine midweek to ensure the level stays in an effective range. If you have to scrub the beginnings of algae bloom off your walls every week, you need to change something in your current routine.

    2. You do not need to add shock after every rain. If you check your chlorine after it rains, it is within normal ranges, skip the shock.

      Brushing does not spread algae; it breaks it up. Think of it like this, the chlorine is Windex, and a window smudge is the algae. If you spray on the Windex, sure it should clear up the smudge, but there may still be residue left. So, what do we do, get a paper towel to wipe it off. Because algae is more stubborn than dust, we use a brush instead.

  5. Algae needs food and phosphates provide algae with the nourishment needed to survive. You want to use a phosphate remover to lower phosphates down below 250 ppm but lower is better. This should keep your pool algae free while also keeping other chemicals at their proper levels.

  6. Hi
    I’ve been struggling with algae all last summer. I have an above ground 10,000 pool. In the end of the season I shocked the pool, vacuumed it to waste and closed it. This year when I opened the pool water was a bit cloudy but clear. I balanced PH and Alkalinity and shocked the pool (2lb for 10k gallons). The next day I brushed and vacuumed and at night added another 1lb of sock. The next day I see light grey substance on the bottom that looks like what I vacuumed to waist in the end of last year after killing algae. The substance is light gray color and decimates when touched. What could it be. Please help I am at a complete loss and desperate. I wish I could post pictures.
    Thank you so much.

  7. Here you will get to know about why does my pool keep getting algae. This article is very informative and helpful for everyone. Before hitting on the other blogs I would request all to give a try here to get the best available content here. The article is much informative regarding work as well. I have seen similar information at one place, you can also see on Poolpac.co.nz

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