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Thread: Black Algae and a drained pool.

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    Black Algae and a drained pool.

    We may at some point in the future drain my neighbours pool.

    There are many plaster delaminated spots where black algae is growing. They cannot at the present time afford a replaster job.

    I am aware of the in-pool treatment with pucks but there are a lot of areas and I do not think it reaches well under the delaminated areas.

    What might be the best method to remove these black algae areas once drained?

    In the past I used chlorine soaked rags overnight and scrubbed with a wire brush, it seemed to work but the algae did come back. The return may have been due to them not keeping the pool in proper balance. Is this the best method or could someone know of a better solution?

    Thank you.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    Re: Black Algae and a drained pool.

    Have you gone through the shock process outlined in pool school? Keeping appropriate FC levels, and circulating the pool water with the pump should take care of your algae issue.

    Unless you are ready to re-plaster, is there another reason you want to drain the pool? If you are, for example, trying to lower CYA, doing several partial-drains might be a better approach.

    Can you post full test results? And maybe pictures?

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    Re: Black Algae and a drained pool.

    Blakej,

    Sorry no pictures I do not feel right about posting other peoples pool's pictures.

    The balance we had two days ago was as follows:

    FC - 7.5 to 8.0 (mustard gas issues in Hawaii)
    pH - 7.7
    TA - 80
    CH - 350
    CyA - 80
    Salt - 3300
    Borates - 0 (Dogs)
    Temp - 78
    CSI - -0.15 (approximate)

    But as stated I doubt if he maintained the pool properly. I am now maintaing it twice a week as the man of the house just had a major operation which may take a year of recovery and his wife does not know how to do it.

    We did do a three day shock about a month ago as at that time his CyA was only 10 ppm, so as you can see he did not keep up with balance tests. The shock helped a little but not that much. Since then I rebalanced the chemicals to the above specs and are maintaining them. Hopefully over time it will slowly remove the black algae with this proper balance.

    The pool is 20,000 gals and has a saltwater generator which runs 10 hours per day.

    The reason we may drain is to remove iron stains. I prefer this method I know many would disagree preferring to leave the pool water in the pool but my personal experience is this results in a longer term stain free pool, others may have different experiences. To anyone who wishes to post a disagreement to that thinking you are welcome, but I will not respond as personal experience using both methods it is now my preferred method, as they say "To each his own".

    Thank you for your reply, hopefully maintaing a proper balance will allow the removal of the black algae, albeit slowly.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    Re: Black Algae and a drained pool.

    Quote Originally Posted by smallpooldad
    Blakej,We did do a three day shock about a month ago
    Black algae is much tougher than green algae to get rid of. It often takes many days of shocking (and daily brushing). My initial thought is that the previous shock was not long enough. I know it is a pain to shock again, but it will be the most effective way to remove your algae issue. When you shock this time, I would use liquid chlorine (rather than pucks) so that you don't raise your CYA anymore.

    Based on the chart in Pool School, you should maintain shock level of 30 FC. During this time, you will need to brush the black algae area often.

    Here are some links that might help:

    pool-school/shocking_your_pool

    pool-school/chlorine_cya_chart_shock

    pool-school/defeating_algae

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    Re: Black Algae and a drained pool.

    Blakej,

    Thank you for the very informative and quick response, your links are very helpful, especially where it mentions not to go too much over on the chlorine.

    By your photo you look a lot younger than either my neighbour or myself, so as far as the scrubbing goes we are going to have to find a person who needs to make some extra money and is fit.

    At least I know what to do thanks to you.

    Aloha.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    Re: Black Algae and a drained pool.

    Haha, I wish I was in Honolulu to lend a hand! I'd imagine the weather is great out there right now....meanwhile it's hailing here!

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    Re: Black Algae and a drained pool.

    Yup,

    77 F up here on the mountain with very few clouds, winds they say at 13 mph, but feels like 5-8 mph, 51% humidity.

    Clear skies over Diamond Head and Waikiki at 80F and beautiful surf waves this morning on the south shore at Waikiki.

    Life's so tough here.

    But honestly we had a lot of rain since January, some of it torrential for days on end. The climate has certainly changed over the last 33 years since I first arrived. We used to get a lot of small showers which we call "Liquid Sunshine" because one cannot see the clouds. This was great for farmers as it supplied just the right amount of rain and drought conditions were rare, so a lot of cattle farming on the Big Island of Hawaii. Nowadays it either pours or no rain at all, which means most of the rain cannot be absorbed by the soil and runs of into the ocean, cattle herds are often at only 10 - 25% of their 30 year ago size as not enough grass grows to sustain them and importing feed into Hawaii is very expensive. Many parts of the islands have been in drought conditions for years.

    And we too had record size hail and small tornadoes here a few weeks ago, nearly unheard of in Hawaii.

    http://www.youtube.com/watch?v=W-SHcpdEYnM

    So while it is still Paradise we do have our issues, but walking my dog around Diamond Head every evening with the bikini scenery makes up some for these minor hardships. My wife says the reason I rescued a racing Greyhound is that it is a "chick magnet" and I should be ashamed at my age, that is so unfair. So if life is getting you down get an ex-racing Greyhound, not smelly, sheds little, typically barks not at all, likes to sleep 20 hours a day, and normally very very friendly especially to ladies as it understands there is good chance of getting a treat from them. Never had a Greyhound before, had many other breeds, but from now on I am a Greyhound person. Mine is Miss Personality Hawaii and I could not be happier. Of course the downsides are you also need to exercise them in the morning as well, mine goes out, rain, storm, or thunderstorm, or no rain, at 5:00 am and at that time there is no scenery as it is too dark. And if no couch to lie on no happy dog; forget your couch it is theirs no matter what you do, unless you want to wrap your couch in barbed wire. Well life cannot always be perfect.

    Aloha and thank you for all your kind help.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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