dark green pool - how do I clean it??

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
chem geek
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dark green pool - how do I clean it??

Postby chem geek » Mon 13 Sep, 2010 02:19

Algaecides for Prevention vs. Killing an Existing Bloom
In the initial post by swimsaveusa, it was stated that chlorine could be used to clear the pool if one didn't mind waiting and that a good algaecide should be used to clear it up quickly. That then started a disagreement on what an algaecide does and PolyQuat 60 was used as an example of a good algaecide. Other options given were a copper algaecide and an algicide/clarifier combo.

Algaecides do kill algae, but at the concentrations allowed in pools most do not do so quickly and for some algaecides they do not kill algae faster then they can reproduce though they do significantly slow down algea growth rates. In the case of PolyQuat, I've communicated with chemists from Buckman Labs (who do make PolyQuat that is rebranded though most manufacturers are in Hong Kong and China) before and it's very clear that the algaecide does a much better job at preventing algae than at killing an existing algae bloom. That does not mean that it does not slow down growth, but it's not going to kill quickly and PolyQuat alone will not completely stop algae from growing under ideal algae growth conditions (nutrients, temperature, sunlight). On the other hand, the polymer is somewhat of a clarifier so if used in conjunction with chlorine it will tend to clear the pool faster, though using a specialized clarifier (along with chlorine to do the actual killing) would do so even faster. Of course, that just moves the problem of dead algae having to be removed from the filter through backwash/cleaning (depending on filter type). With chlorine alone, one can kill algae and also oxidize it to get rid of it, but this can take longer. It's really more of a cost/convenience trade-off. A picture sequence of a pool with algae getting cleared up using chlorine alone in around 4 days is shown here . One should not forget about brushing during the process and vacuuming/scooping if there is a lot of debris.

Algaecides and High CYA Levels
If the algae grew in the first place because the CYA got to a high level and the FC had not been raised proportionately to prevent the algae growth, then using chlorine alone can be impractical due to the very high FC levels needed to kill the algae and to clear the pool in a reasonable time. It's certainly possible to do, but if the CYA were 200 ppm, then even 40 ppm FC would be a fairly slow kill and clearing. Besides, one really needs to address the high CYA level anyway so doing a partial drain/refill is going to be needed so one might as well do that sooner rather than later. With a lower CYA level, a lower FC level can be used to kill and clear the algae, regardless of whether this is helped out by algaecides or clarifiers. When the FC is around 40% of the CYA level which is a shock level for reasonably fast killing and oxidizing, this is equivalent in active chlorine (hypochlorous acid) concentration to having an FC of around 0.6 ppm with no CYA.

The discussion about some algaecide products getting around the high CYA level is correct since that is the primary purpose of both ammonia-based and sodium bromide algaecides. These products work because the ammonia combines with chlorine to produce monochloramine while the bromide gets oxidized by chlorine to become bromine and neither monochloramine nor bromine are affected by CYA so are at full-strength to kill algae, regardless of CYA concentration (unlike chlorine). This is just a band-aid solution since you still have high CYA levels to deal with when you are done.

Taylor Guide and Chlorine-Resistant Algae
The Taylor guide that comes with their test kits was mentioned. First off, the Taylor guide gives absolutely no guidance about how the active chlorine concentration (hypochlorous acid) that does the actual killing of pathogens and algae and oxidizes bather waste is related to the FC/CYA ratio. They state absolute FC levels that should not be independent of CYA level. For example, yellow/mustard algae can in fact be inhibited when the FC level is roughly 15% of the CYA level which is higher than that for green algae at an FC of around 7.5% of the CYA level. Usually one wants to completely get rid of yellow/mustard algae rather than maintain higher chlorine levels and this is harder to do but can be done -- the shock level is higher (around 60% of the CYA level), must be maintained at this high level longer, and one must get behind light niches and under ladders and put in equipment (poles, etc.) to ensure a thorough kill. As with most algae, an ounce of prevention is worth a pound of cure.

Then there was some discussion about chlorine-resistant algae and whether there is algae that will not be killed by chlorine and when chlorine levels are low then algae can begin to develop a tolerance. Chlorine is not like an antibiotic with only a single mode of action that can be circumvented via mutations to slightly alter cell processes. Chlorine will combine with (in a substitution reaction) and often oxidize many nitrogenous organic compounds including most amino acids, proteins, enzymes, DNA, etc. There is no tolerance that is built up from exposure to chlorine as there is no single or small number of mutations that would result in chlorine resistance. The chlorine molecule looks very much like water (both are neutral molecules and polar and small in size -- water is HOH while hypochlorous acid is HOCl ). Now it is true that if one uses a lower level of chlorine that the heartier already existing species may still survive so a complete kill is not achieved, but that's not due to any sort of developed resistance that came from chlorine exposure. Pathogens that are more resistant to chlorine are more resistant to environmental stresses in general and developed those over a very long time. Protozoan oocysts (e.g. Giardia, Cryptosporidium) are resistant to chlorine, but had their tough oocyst exteriors long before any exposure to chlorine and was an evolutionary development to surviving a harsh environment outside their hosts.

Other Algaecides
The most effective algaecide for all types of algae is copper ions, but the level at which copper kills effectively gets dangerously close to the level at which copper can stain pool surfaces, especially plaster. Yes, one can lower the pH to minimize such risk, but the copper is not easily removed from the pool and if the pH rises for any reason, staining can occur. The myth of having the copper sequestered or complexed is that only the free copper ions are able to kill the algae and it is those same free ions that will stain. The sequestering or complexation just acts like a copper buffer so will replenish that which may get used up caught in algae and filtered out, but it does not prevent staining unless it makes the dose so low that it may not be very effective (again, depending on pH).

Phosphate removers weren't mentioned, but should be seen in the same vein as Polyquat algaecide in that it can significantly reduce the rate of algae growth but may not prevent it completely. This is because such removers do nothing for organic phosphates and algae can still use those to grow, though their uptake is slower so the growth isn't as fast as with inorganic phosphate (i.e. orthophosphate).

Many Ways to Manage Pools
There are many different ways of maintaining pools and there isn't one that is "right" with all the others being "wrong" -- they just vary in convenience and price. Yes, there are tens of thousands of pool owners who maintain their pools using chlorine alone inexpensively without the need for algaecides, phosphate removers, clarifiers, flocculants or weekly shocking at The PoolForum and Trouble Free Pool as well as this site, but not everyone wants to add chlorine every day or two (if they don't have a saltwater chorine generator or an opaque pool cover). If someone wants to use Trichlor pucks/tabs for the convenience, there is nothing wrong with that, but they should realize that if they want to prevent algae growth they either need to 1) raise their FC target as the CYA level climbs or 2) dilute the water to keep the CYA level in check or 3) use an algaecide or phosphate remover to slow down algae growth rates (which works up to a point but if CYA gets really high even this won't work) or 4) shock the pool weekly to partially make up for too low an FC/CYA level during the week or 5) be lucky having a pool poor in algae nutrients.

Richard


James Watson

dark green pool - how do I clean it??

Postby James Watson » Mon 13 Sep, 2010 15:40

+10 for chem geek

I think that it's important to emphasize that this is not an ordinary outbreak of algae.

not had the filter on once in the last 18 - 24 months, maybe longer... The water is the darkest of green colors.


This is extremely thick algae that is going to be coated on the walls and bottom as well as in the water. There is no way that algaecide would clear this.
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dark green pool - how do I clean it??

Postby danneva » Tue 14 Sep, 2010 06:12

swimnsaveusa wrote:I would love to hear what you do when you end up with a strand of chlorine resistant algae since according to you algaecides don't work. :lol:


Add algaecide to your pool in the morning or when bright sunlight is shining on the pool. Algae thrive in light and adding the algaecide during that time encourages the plant growth to consume more of the algae killer. Vacuum the bottom of the pool each evening to get rid of dead algae. Shock the pool according to your shock treatment instructions if the algaecide fails to work.
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dark green pool - how do I clean it??

Postby duraleigh » Tue 14 Sep, 2010 08:08

Algaecides are typically far better at preventing algae than killing it.

They will certainly kill some organics but, as James Watson has indicated, if you want to clear a pool, particularly a really nasty one, chlorine is far and away the best algae killer you can use.
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chem geek
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dark green pool - how do I clean it??

Postby chem geek » Tue 14 Sep, 2010 19:20

danneva wrote:Add algaecide to your pool in the morning or when bright sunlight is shining on the pool. Algae thrive in light and adding the algaecide during that time encourages the plant growth to consume more of the algae killer.

Algaecides vary in their mode of action and for linear quats and PolyQuat, algae do NOT "eat" it. These quaternary ammonium compounds (QAC) work by interfering with cell membranes and ultimately ion transport by causing cell leakage and membrane damage. They do not enter the algae cell to slow down algae growth and do not require the algae to be growing, have active photosynthesis, or reproducing in order to be effective. This scientific paper talks about the mode of action of QAC against a particular bacteria, but the same mode of action occurs with algae as well.

Copper ions, on the other hand, do enter the cells, but do not require the algae to grow (reproduce) to kill algae as they interfere directly with chemicals inside of the algae cells.

Ammonium products (e.g. ammonium chloride) form monochloramine when chlorine is present and this IS taken up by algae cells as part of metabolic growth (as the molecule looks a lot like ammonia) so might have some greater killing effect during the day, but I can't find any definitive scientific source confirming this.
green pool help

dark green pool - how do I clean it??

Postby green pool help » Mon 23 May, 2011 10:16

ok soo im new to this but my water was very dark green. I talked to a pool guy and he told me to add 10 lbs of shock to my pool. I have now added 16 lbs and it is lighter but not right yet. I am seeing people talking about pouring bleach into the pool sorry again im new to the pool thing are you meaning straight bleach i would like clean clothes or my bathroom with. Heck that is way cheaper then shock. lol. please let me know and i will try that. if so can i pour in 2 bottles and wait a couple days to see what that does of course no one will be swimming until this problem is fixed. just dont want to mess up my liner. Thanks green pool help
chem geek
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dark green pool - how do I clean it??

Postby chem geek » Mon 23 May, 2011 22:03

Read Defeating Algae in the Pool School. Note that if your CYA level is high, you may want to do a partial drain/refill first to lower it so that it will take less chlorine to kill the algae and to maintain the pool going forward.
eli

dark green pool - how do I clean it??

Postby eli » Sat 11 Jun, 2011 08:12

Lisa020270 wrote:We just bought a new home with an above ground pool that looks as if it has been laying in neglect for a while. The water is so green I can dye clothing in it.

I am a first time pool owner. What do I do to clean it?

All replies welcome. Respond to Lisa020270 at aol.com

I've been trying to clear my pool for 3 weeks from dark green to now light cloudy green i have a 27foot round what can i do now I'm about to emty it please help
Guest

algea

Postby Guest » Mon 13 Jun, 2011 13:11

ktownkid wrote:Pool is green tried everything 200 in chemicals so far. thinking about getting rid of pool, but reading other peoples troubles and learning that maybe bleach is the solution, I want to know is it the answer I've been looking for. I have a 18 foot above ground pool. How much should I use in it if it works. signed Like green in my wallet.
andyg0lf81

dark green pool - how do I clean it??

Postby andyg0lf81 » Tue 21 Jun, 2011 19:55

Here, I was asking the question the instead of spending all the money on the stuff. why not just drain the pool and pay the city for the water. would it be less cost?

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