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Thread: Black Algae/Waterfall

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    Join Date
    Feb 2013
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    Gilbert, Arizona
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    Black Algae/Waterfall

    I am a relatively new pool owner(pebbletec), and with these super hot AZ days we must have let our FC drop too low for our CYA level, and now have a few black algae spots on the bottom of the pool. We used a pool pumice to scrape them up & began the shocking process with liquid chlorine last night. My concern now is that the waterfall seems to have been the source. The boulders at the base of it were growing with algae. The problem is that part of the area is not always submerged, and the boulders have nooks and crannies that are hard to brush with a steel brush, and even a chlorine tab. Any suggestions on eliminating all traces of algae in those hard to reach places above the water line so we can avoid reintroducing algae after shocking?

    I have read to frequently clean the filters during this process, yet the pump must run 24/7 We have cartridge filters. Should I just clean them when the shocking process is over, or would it be better to turn the pump off for a couple hours to thoroughly clean the cartridges?

    CYA has been difficult to pin down. Leslie's always came in around 70-90, but home test showed 60. I think I may have been doing it incorrectly, and my recent test (while shocking) showed 45-50. We dropped the PH to 7.2-7.4 last night, but this morning we have TA 90, CH 360, FC 27.5/.5CC...too high? Damage?

    We also have a regular problem with PH rise, possibly due to SWG with spillover/water features. I have yet to understand how PH impacts algae growth, and whether borates would be beneficial for us. We readily climb to 7.8 and have to add acid to get it back into range. I realize this is a different issue, but any advice is greatly appreciated. I'm still trying to get my bearings with all of this & ironically I thought I was doing a pretty good job - ha, lesson learned!
    14,000 gallon, IG, pebble-tec, cartridge filter, 1 HP Hayward Super Pump II K48L2N104, built 2007, spa/spillover, waterfall, AquaLogic SWG, in-floor cleaning system

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    Mod Squad zea3's Avatar
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    Re: Black Algae/Waterfall

    Hi, welcome to TFP! Its ok to turn off the pump long enough to clean the cartridges. Just clean them when the return flow is significantly reduced. You can read the result of the CYA test several times to help you pinpoint the test result. Stand outside in strong sunlight with your back to the sun holding the tube at waist level. Pour in the solution until you no longer see any trace of the dot at the bottom of the vial. You can then pour the solution back into the mixing bottle, then back into the test vial and read the result again. You can read the test 3-4 times to help you get the hang of it.

    Scrub the rocks as best you can. It may help to get a pump up sprayer and spray down the rocks with shock level pool water several times a day.
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    Re: Black Algae/Waterfall

    Regarding your pH rise. I'd shoot for getting that TA down to about 60, then see what happens with your pH rise. If it is still there at 60, borates will most likely help. They may also help with your algae problem on the rocks, but there's no guarantee.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Join Date
    Feb 2013
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    Gilbert, Arizona
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    Re: Black Algae/Waterfall

    Thank you for the replies. I will try spraying the recessed areas with shock level water, and once we get this issue solved, I will have to experiment with getting that TA down. It rises so quickly, I can't imagine getting it below 80! Should be a breeze after algae.
    14,000 gallon, IG, pebble-tec, cartridge filter, 1 HP Hayward Super Pump II K48L2N104, built 2007, spa/spillover, waterfall, AquaLogic SWG, in-floor cleaning system

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    Modawg2k's Avatar
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    May 2013
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    Re: Black Algae/Waterfall

    Hey any update? I'm in the same boat here with with a rock water feature that is riddle with algae on it from improper chlorine tracking and I also have black spots starting to form on my pebble.
    ~15k gallons, 3'-5'-4' Figure 8 Shape In Ground
    Wetedge Satin Matrix Interior (Pebble)
    Paramount In-floor System
    Pentair IntelliFlo VS 3050, Pentair Triton II TR100 Sand Filter
    Pentair Intellichlor IC40 SWG

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    Join Date
    Feb 2013
    Location
    Gilbert, Arizona
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    Re: Black Algae/Waterfall

    Sorry, just saw your question. Yes, great success! However, I would urge caution when brushing the waterfall! I had read so many horror stories about hard to eradicate algae that we lost a bit of the surface in spots. Shocking the pool for about five days and testing each day solved our problem and we haven't seen any algae since.
    14,000 gallon, IG, pebble-tec, cartridge filter, 1 HP Hayward Super Pump II K48L2N104, built 2007, spa/spillover, waterfall, AquaLogic SWG, in-floor cleaning system

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