Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 4 of 4

Thread: Algae in a covered hot tub - wasn't expecting that

  1. Back To Top    #1
    bridgman's Avatar
    Join Date
    Mar 2014
    Location
    Bowmanville, ON Canada
    Posts
    461

    Algae in a covered hot tub - wasn't expecting that

    After keeping the same water in the hot tub over the winter, I noticed it seemed to be getting a bit cloudy.

    The water surface is >95% covered with wood/aluminum, CYA was reasonable (25-30) and I had been "fairly diligent" about checking & adjusting FC level daily so I figured it was the particularly dismal cloudy light rather than anything wrong with the water. Dragged the little Intex filter pump up from the basement and ran it for a few hours -- it didn't appear to make any difference, so in my little mind that reinforced the theory that it was poor light rather than poor water.

    We finally got a sunny day, so I pulled off the cover and saw a noticeable greenish tinge. Not swampy, but not clear either. Colour isn't as obvious in a wooden tub as it is in a nice light-coloured pool, but with bright sun there was no doubt. Thought about SLAM-ing just to get some experience with it, but eventually decided to drain and refill.

    As the water level dropped (it's about 3-1/2 feet deep when full) I was surprised that the wood grain on the seats and bottom of the tub was not becoming clear. I had assumed the only problem was cloudy water, but when I tried brushing a big plume of white powder (presumably dead algae) came up from the bottom, and the wood grain was clearly visible under the powder. Geez that's a lot of dead algae -- guess the FC had been high enough to keep it from going swampy but there was a constant grow/kill cycle going on.

    Finished draining the tub while brushing constantly, then scrubbed with diluted bleach & refilled. I'm being more careful about checking FC daily rather than "daily except when I forget", hopefully that should prevent future relapses. I couldn't believe how much dead algae formed even in my little tub -- I have a lot more sympathy now for people waiting for their filter to clean up a 20K gallon pool.

    Anyways, the main point that was reinforced for me was the difference between "shock" and "SLAM" -- FC level was getting up to shock level from time to time (when I was going to be away for a few days) -- apparently all that did was turn most of the live algae into dead algae but leave enough algae for growth to continue.

    The second revelation for me was that I *really* need to look harder into growing specialized algae for biofuel production. I was really impressed how enthusiastically it grew
    Cedar hot tub, 680 US gallons - Snorkel wood-burning heater, canoe paddle, "offline" Intex 1000 GPH pump/filter with skimmer

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Algae in a covered hot tub - wasn't expecting that

    You made some good revelations there
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  3. Back To Top    #3

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,084

    Re: Algae in a covered hot tub - wasn't expecting that

    Very nice, informative post......Thanks!
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  4. Back To Top    #4
    bridgman's Avatar
    Join Date
    Mar 2014
    Location
    Bowmanville, ON Canada
    Posts
    461

    Re: Algae in a covered hot tub - wasn't expecting that

    I still don't fully understand how the algae grew in the first place. There's only a tiny sliver of light getting in around the "fence" between stove and bathing area, guess that must be enough to let the algae grow in a slice of water.

    Every time I go near the tub now I hear "Return of the Giant Hogweed" playing in my head. "Strike by night !! They are defenceless. They all need the sun to photosensitize their venom"...
    Cedar hot tub, 680 US gallons - Snorkel wood-burning heater, canoe paddle, "offline" Intex 1000 GPH pump/filter with skimmer

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •