Green algae on gunite walls and bottom

186logic

Member
Aug 6, 2019
13
NY
Every year I open pool around Memorial Day and don’t have a problem until about late June. It gets progressively worse until closing. I keep chlorine/ph/chemistry perfect, brush regularly, shock, backwash when necessary and vacuum. There are a lot of trees/vegetation around the pool and it’s very shady with approx only a quarter in the sun all day. I haven’t resorted to algaecide yet as I’ve heard if chlorine is kept right that’s all you should need. I think in the past when I had a pool guy do maintenance he solved problem by keeping chlorine really high, which I really don’t want to resort to.
Am I missing something or are my only options algaecide or high chlorine and if so which is better? BTW pool water is pretty much always sparkling clean...never really gets green. Thx
 
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Every year I open pool around Memorial Day and don’t have a problem until about mid June. It gets progressively worse until closing. I keep chlorine/ph/chemistry perfect, brush regularly, shock, backwash when necessary and vacuum.
Welcome to TFP! :swim:

How do you test and who says the numbers are "perfect"? What source are you using for "perfect numbers?

What do you use to add chlorine?

What are you using to "shock"?
 
Now, what you are describing is a typical "northern" pool. You float 3" tabs in the pool, you shock every Saturday morning and keep the chlorine at 2 - 4. You then take a sample to the pool store and they say it's "perfect".

Is this you?
 
This really only happens when there isn't enough chlorine to keep the algae from forming
which is usually a result of not having a proper test kit to know what your pool needs.

Getting a testkit is the first step. If you follow the tfp way of things, you won't have this problem again.

I have not had any algae in my pool for over 5 years using the methods taught here.
 
Now, what you are describing is a typical "northern" pool. You float 3" tabs in the pool, you shock every Saturday morning and keep the chlorine at 2 - 4. You then take a sample to the pool store and they say it's "perfect".

Is this you?
Yes for the most part. I use a chlorinator for 3” tabs and keep it between 2-4. When shocking I bring it up to around 10...but not on Saturday since we want to swim in it lol. I use aquacheck 7 strips and don’t really take sample to store anymore since they read the same as the strips 90% of the time.
 
Yes for the most part. I use a chlorinator for 3” tabs and keep it between 2-4. When shocking I bring it up to around 10...but not on Saturday since we want to swim in it lol. I use aquacheck 7 strips and don’t really take sample to store anymore since they read the same as the strips 90% of the time.
Well, now is the time to make a decision, keep following what you have been doing follow our methods.

First, I will tell you, it didn't get algae overnight and it will take time to clear. But, we can teach you how to get it sparkling and keep it that way for a lot less money than the pool store.

Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. Plus, the results of their "testing" is used to convince you that you need to buy things. Why do you think that testing is free?

But, what can you do?? We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit. Order a TF-100 Test Kit ™ and at least include the XL Option . That will give you what you need while you are clearing the pool, and probably enough reagents for a couple of years normal use. Please don't go back to the pool store for a test kit. To effectively practice the TFPC methods, the FAS/DPD chlorine test is essential. The TF-100 Test Kit ™ has this test while very few other kits do. The kits sold at the pool store generally won't won't cut it, but be careful pool store employees are known to say “it's the same thing”. Generally it's not!

The test strips you have are what we call guess strips. You can't trust teh results they give. Please don't go to a pool store for a test kit. To effectively practice the TFPC methods, the FAS/DPD chlorine test is essential. The TF-100 Test Kit ™ and the K-2006 have this test while very few other kits do. The kits sold at the pool store generally won't won't cut it, but be careful pool store employees are known to say “it's the same thing”. Generally it's not!

I'll teach you a secret. That shock and those tabs are about 50% stabilizer. Your pool is over stabilized (too much CYA/stabilizer). Everyone tells you that they are the easiest way to get chlorine in your pool. They are. But, they don't tell you (or really don't understand) that the 3" tabs also add CYA (also known as stabilizer or conditioner) to your pool. All pools need stabilizer, but not too much. Others here can give you the scientific details if you want, but lets just say CYA locks the ability of chlorine to sanitize. The more CYA you have the more chlorine you need to keep in the pool to keep algae at bay.

Until you get your kit, each day I want you to put one bottle of bleach (yes, the same stuff you use for laundry) in the pool with the filter running. Be careful, it needs to be plain bleach, no scents, no EZ-Pour and none of the new Cloramax or laundry enhancing formulas.

While you wait for it to get delivered, you have a homework reading assignment. Start with these:





So again, welcome to TFP!!
 
I forgot to mention I use cal hypo to shock and CYA reading is 50ppm which I thought was good? Can I use cal hypo instead of bleach?
Well, you said this before:

I use aquacheck 7 strips and don’t really take sample to store anymore since they read the same as the strips 90% of the time.

So, no - we do not believe the results of test strips or pool store testing.

As to CalHypo for a SLAM, no.

First, CalHypo adds Calcium to your pool. When this gets too high it results in scale. Plus, it is slow acting. You toss it in and it takes time to dissolve before it starts acting. Liquid chlorine (bleach is liquid chlorine) starts working immediately.

To quote Dave here at TFP:
Throughout TFP, you will read that we suggest certain levels that good science and practical experience has taught us fall within safe ranges.

Further reading of posts here will draw you to the inescapable conclusion that these guidelines work.......in thousands and thousands of pools worldwide.

You may or may not choose to use these methods and guidelines or you may use some and not others. Our goal is to teach you what has been proven time and time again and then let you use that information to your benefit.

So, to be honest, you can do what you want. But, we don't recommend it.
 
Our water here has no hardness so the extra calcium in cal hypo is actually a good thing.

Is it likely that 3” tabs could raise CYA levels above 70 ppm when it’s only added during the 4 months it’s open and no other stabilizer has been added?
 
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Our water here has no hardness so the extra calcium in cal hypo is actually a good thing.

Is it likely that 3” tabs could raise CYA levels above 70 ppm when it’s only added during the 4 months it’s open and no other stabilizer has been added?
Actually, "extra" calcium is never a good thing. Vinyl pools don't need any and gunite/pebble/concrete pools need some, but not too much.

As to the CYA, it's all math. How big is the pool and how many tabs do you use in a season? In a 10,000 gallon pool, each tab adds 3.3ppm CYA. You also have to remember that any water left in the pool over the winter carries over the CYA. It is not unusual for them to be fine for the first few seasons, but as the CA slowly builds up they start having algae problems. Pool stores will tell you this is normal, that is what they have many different magic potions in the store to combat algae. When it finally gets to the point that nothing works they will tell you your water is "stale" or you have "chlorine lock". At that point they will recommend a total refill of the pool.

It's easier to just stay ahead of the CYA.

Please edit your signature and add the following information so we can better frame our answers to you.
  • List what test kit you use to test your water
  • The size of your pool in gallons
  • If your pool is an AG (above ground) or IG (in ground)
  • If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass
  • The type filter you have (sand, DE, cartridge)
  • If you know, tell us the make and model of your pump and filter.
  • List any other equipment you have: SWG, second pump, etc.
  • Please mention if you fill the pool from a well or are currently on water restrictions

Information in your signature will show up each time you post and it makes advice more accurate as we know what equipment we are dealing with.
 

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Done. Plaster, so I need calcium since my water has none.
Does CYA burn off or degrade? Guessing I lose at least 1/3 pool volume between closing and opening releasing some CYA.
I’ve always been suspect of the college/high school kids that do the testing at Leslie’s, but them telling me “water’s perfect” is counterintuitive to selling me unnecessary product.
I’ll get the test kit you recommended and I’m curious to compare readings with the strips
 
Done. Plaster, so I need calcium since my water has none.
Does CYA burn off or degrade? Guessing I lose at least 1/3 pool volume between closing and opening releasing some CYA.
I’ve always been suspect of the college/high school kids that do the testing at Leslie’s, but them telling me “water’s perfect” is counterintuitive to selling me unnecessary product.
I’ll get the test kit you recommended and I’m curious to compare readings with the strips
Yes, your plaster pool should have CH 250-350

While CYA does degrade, it does it very slowly, maybe 1 - 2 ppm per month

You have a large pool, so one tab when fully dissolved will raise your CYA 0.7, but for a pool that large you need a lot of them.

If you drain the pool by 1/3 at closing you will eliminate 1.3 of the CYA you have accumulated during the season. But, as I said before it slowly accumulates from season to season.
 
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Update:
After reading the trouble free FC/CA recommendation chart I adjusted my FC up as I at times would let it drop to 1 ppm thinking it was OK based upon 1-3 ppm reco. I’ve kept it at 5-7ppms and have had no more algae problems for the past month.
What FC level does TFP consider dangerous for bathers?
Thx for all the help
 
What FC level does TFP consider dangerous for bathers?
You can safely swim in a pool as long as the FC is above the minimum and at or below SLAM level based on your CYA. You must also be able to see the bottom of the pool in the deep end of the pool.
 
I’ll get the test kit you recommended and I’m curious to compare readings with the strips
That really doesn't help you and might hurt you. If the comparison of the strips and the test kit match, will you go back to the strips? That just won't work.......strips have time and time and time again have proven to be unreliable. The bulk of what we teach is based on precision testing and the two kits we suggest will provide that.

I would encourage you to adopt TFP methods.......they are painless enough and you will never look back.........I promise. The stuff you can learn on this forum is scientifically solid and will help you manage your pool correctly for years and years.
 
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