yellow/mustard algae

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tracyd

Well-known member
Aug 11, 2013
52
North Kingstown, RI
I have been looking all over the internet for the answer to a question. How do I know if yellow/mustard algae is dead? I slammed the pool and kept it at above shock level for 48 hours. I also initially used yellow out. It has been 5 days, appx 40 gallons shock = 80 gallons bleach. My FC level is maintaining/not dropping, the water is pretty much clear until I scrub the bottom/sides of pool. I scrubbed the pool 3x/day throughout the process(I have blisters to prove it). I have a DE filter which I have backwashed and recoated 5-6x. Does it just take time to clear up? Im still getting a "brown dusty film" on bottom and sides of pool- MUCH less every day. Does the algae change to a different color when dead? Im really paranoid the algae will come back as it was alot of work to get to this point. Please help!

40,000 gallon L shaped pool
vinyl liner
 
Do you know your CYA (conditioner/stabilizer) value from a reagent based test?... Not a computer.

If your CYA is 100+ ppm, all algae, green, black or mustard, will grow in pools with high FC.
 
Welcome to the forum. :wave:
I slammed the pool and kept it at above shock level for 48 hours.
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No you didn't SLAM. By it's definition, SLAM removes all the living organics in your pool. You confirm that with an OCLT (Pool School).

While you certainly elevated your chlorine to SLAM level, you have not completed the SLAM process. Your pool may or may not clear up if you still have algae in your pool

Performing the OCLT will tell you that the SLAM process is complete.....you really may have stopped too soon.

Can you post a complete set of test results including CYA.
 
Duraleigh, Thats my question.... if I do a OCLT and the FC loss is <1 then I can conclude that the algae is dead?
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Probably yes but the SLAM process is complete when...
1. Your pool water is sparkling (your visible debris needs to be cleaned up....it's surely dead algae.
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.

By far, the most common cause for failure when you SLAM is the rush to stop using so much chlorine....it's human nature and I understand.

However, you are cleaning up a pool that has been neglected for a good while if you have used that much chlorine to this point.

Brush, vacuum run your pump 24/7 and do everything you possibly can to get the pool pristine before you allow your chlorine to drift lower than SLAM level.

The SLAM begins with precise test results and it ends the same way....regardless of the chlorine consumption in between.
 
Welcome to tfp, tracyd :wave:

tracyd said:
Unfortunately, I dont have one of those "black dot" CYA tests just the test strips(its on my list). It appears to be 40.
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Since your cya test is based on test strips, you can almost be certain it's not 40...test strips are not reliable for most measurements and especially not cya. In order to know if you are using a high enough FC level, you need a reliable cya test. Read this pool school article for an appropriate kit: http://www.troublefreepool.com/pool-school/pool_test_kit_comparison

How do you know you have mustard algae?
 

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I just called my local pool store to ask if they carry the CYA black dot test in their store and the woman asked "why do you need that?". I told her my whole story/yellow algae. She said I shouldnt use liquid chlorine I should have used Sodium Dichlor stabilized powered shock. I went into the whole raising my CYA level and chlorine lock/ also afraid that powdered chlorine in that much quantity would damage my liner. She said it was nonsense, she has been doing this for 22 years. Am I reading into the whole CYA level/Cl relationshipn too much?
 
She is completely wrong and doesn't know what she is talking about. Yeah, 22 years of making profits selling people chemicals they do not need. Selling stabilized chlorine products (Trichlor and Dichlor), having CYA rise in the pools, some such pools getting algae, people buying more "shock" and other products to help clear their pools including clarifiers, flocculants, enzymes, algaecides, phosphate removers, etc. and weekly shocking. The chlorine/CYA relationship was definitively determined nearly 40 years ago in this paper and has been proven to be true in numerous scientific peer-reviewed papers in respected journals as listed in the "Chlorine/CYA Relationship" section of the first post in the thread Certified Pool Operator (CPO) training -- What is not taught and has been proven in tens of thousands of pools on this and other forums.

The powdered chlorine would not damage your liner any more than any other source of chlorine unless you dumped it in one place and it settled to the bottom before dissolving. Dichlor dissolves quickly which is probably why she didn't think it was a problem. Cal-Hypo would dissolve more slowly, but again, if one adds chlorine slowly over a return flow and lightly brushes the area where one added it, then it gets fully mixed and will not cause any problems with vinyl. This is also the safe thing to do with chlorinating liquid or bleach since it is denser than water until it gets mixed.

If you have yellow/mustard algae, you'll need to get into the shadier places it likes to hide such as behind light niches and under removable ladders (if any). Read the Pool School article on Mustard Algae.
 
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