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Thread: Pink Algae

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    Pink Algae

    21,000 gallon pool with SWG (new this season) run for 8 hours a day.

    I've had this problem with "pink algae" off and on ever since we got our pool over 6 years ago. I've used "Yellow Out" which was recommended by my local pool store with some success but the instructions tell you to basically shock the daylights out of the pool so that might actually be what is doing the trick!

    This year we got a SWG and after a few initial problems (too much salt for starters) it has been working great. I got a DPD test kit and have been checking the FC and PH levels pretty religiously all summer. I've found that the SWG took a LONG TIME to get the FC level up to snuff but once it caught up I was steadily reducing the setting to keep the FC levels reasonable. Once I got the FC levels up using the SWG I stopped shocking the pool. The FC levels have been about 2-3 pretty much all the time since. PH has been consistently 7.6. The other day I decided to add some liquid chlorine to shock the pool for the first time in weeks. Added about a half gallon of 6% liquid chlorine. I'm always looking for signs of pink algae when checking on the pool and I found some just starting yesterday. It was showing up just around the edges of the return jets and I can see a little in the liner seams in the deep end.

    I wonder if the problem starts less because of the chlorine level (which has been pretty high all summer) and more because of our constant use of the solar cover. It's been a bit cloudy and cool over the past week so we haven't been swimming much. The cover is a dark blue which probably doesn't let much sunlight in. I seem to recall that whenever we get pink algae it is usually close to the end of the season when we don't use the pool as much and the solar cover is on more to keep the temperature up.

    I thought I'd post here to see if anybody else thinks the solar cover is a source of the problem. From what I've learned from this site, if the sunlight can't get to the water, then the chlorine can't be as effective at oxidizing the bacteria and the pink algae could be taking advantage of that.

    I'll do a more thorough test tonight in case one of the other measurements is important (CYA, Alkalinity, etc) and post the results here. I suppose I should do a total chlorine test to get the CC number. That would be quite important here I'm sure.

  2. Back To Top    #2
    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Pink Algae

    A full set of numbers will help a lot.

    Which test kit do you have? The FAS-DPD is the one that's recommended. Don't be fooled by the DPD if it doesn't have the FAS- in front of it.

    Have you read Pool School? If not I'd suggest wandering on over there and take peek. If you have, well, just go ahead and read it again.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

  3. Back To Top    #3

    Re: Pink Algae

    I think it's the FAS, it's the big kit with the water wheel and the booklet. It was around $65-70 if I remember correctly. I had to order it online since none of our pool stores carry it, they all use the strips to do their customer water tests! I can test for everything I could ever want with it (except salt level). The past few times I tested alkalinity, it was in range (I don't remember the number though). I've tested for CYA and that was also in range. I try not to test for that one too often as it uses A LOT of the test kit supply to perform (it comes with at least two of the white bottles maybe three). I think I have enough for one or two more tests. Since the season is almost over, I suppose I can spare it to see if it's low. I don't use stabilized chlorine and haven't added any CYA since the last test so I doubt that it will be any higher than before . I haven't tested acid demand in a while since the PH is OK. I did a calcium hardness test and that was in range according to the booklet.

    I read the pool school a while ago. You're right, I should probably take another look.



  4. Back To Top    #4
    frustratedpoolmom's Avatar
    Join Date
    May 2007
    SWSuburban Chicago, IL

    Re: Pink Algae

    This is what the DPD kit (K-2005) looks like:

    This is the kit with the FAS-DPD (K-2006 - which can test chlorine levels up to 50ppm):

    If your DPD test only tests up to 5ppm using this comparator tube:

    then you have a "complete DPD" test it, not the FAS-DPD test kit.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    Perfectly Clear Pool Service, Find me on Facebook!

  5. Back To Top    #5

    Join Date
    Jan 2009
    Cupertino, CA

    Re: Pink Algae

    A quicker way to tell the difference: FAS-DPD uses powder plus drops, DPD uses just drops.
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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