Chlorine or Free Chlorine Green Pools

by Mark

I have a green pool at start up of the season. I shocked, then put in algaecide, and vaced a few times it is not the dark green/black any more but a light-green and ver cloudy. I am trying to figure out if the algae is alive or not.

My total chlorine number is 12 and has been for a while. But my Free Chlorine is low (less then 1). If I keep this situation will that kill the algae? (ie does the total chlorine or the free chlorine kill algae?).

Other chemicals are in the right spot, pH a little high though(7.8)

FYI: I often have a phosphate problem with the pool also (evergreen trees nearby)

Am I ok leting this take it's course and having the filter do it's work (with more scrubbing and Vacing) or do I need to do something to free up that Chlorine?



Thanks for the question Mark

I'd like to have the rest of your chemical readings:

CYA (cyanuric acid/stabilizer), Alkalinity, Calcium Hardness, and Metals (iron and copper).
It makes troubleshooting much easier and the process of clearing up your pool will go much faster.

You can get this done at your local pool store. Without these numbers I'm just guessing at what the problem is. The other readings play a factor into how you will approach clearing up your pool.

The free chlorine (FC) kills the algae. The total chlorine (TC) is the sum of the free chlorine plus the chlorine that's already been used up. That's called combined chlorine.

Remember that algaecide is used for preventative maintenance only. It's not used to kill already existing algae. You can use it to augment the chlorine that's already in the pool, but not to actually kill the algae and clear up the pool.

Concerning the phosphate remover, I'd encourage you to be very careful with that. Only under extreme conditions or circumstances should you need to use a phosphate remover. It can cause more harm than good in the long run.

Here's a post about that. A little long but worth the read. Be sure to read the comments on the 2nd page:

High Phosphates Over 1000 & Cloudy Water

The chlorine is already in the pool but is consuming the algae. The CYA and other readings will show how to handle your situation because each pool is different and has different readings.

Get back to me with the chemical numbers and I'm sure I can help.

Hope this helps and have a great Summer.


Comment By Mark
Date: June 8, 2012

Thanks for the quick reply.

I was puzzled because my reading of the chems were different than the store's (when I did strips and liquid testing). But 2 hours ago I found that my alkalinity was down and the ph was high, so I balanced that out (adding alkalinity and then muriotic acid)

I am going to shock it (since I can see the chlorine levels on my tester now) and re test tomorrow. The pool place did have my cyn low, or at 0, so I added stabilizer too.

Hopefully with the pump on, I can get a clear story tomorrow.


Comment By Robert
Date: June 8, 2012

It can get confusing when you get two different readings. If the pool store isn't using an electrical analysis machine, they're probably using a K-2006 kit. This requires swirling that takes some technique to get a good reading. I taught about 30 lifeguards at the Y on how to use the 2006 kit and even while taking readings each hour, it still took them a couple weeks to get it right. I've been using the K-2006 kit since 1999.

Don't spend extra money on any kind of "conditioner" or "extra special stabilizer". You can use Dichlor chlorine. This is a stabilized form of chlorine. Once you reach the 30 - 40ppm CYA mark, stop with Dichlor and go back to regular liquid chlorine.

If you don't have a tab floater, you can pick one up for
about $12. They'll last for years. Never put tabs in the skimmer. Even with the pump off they keep dissolving. When the pump turns back on the system gets a huge blast of acidic water.

Be careful when using Dichlor as it can get out of hand quickly. For every 10ppm of chlorine added with Dichlor, you'll raise the CYA by 9ppm. For every 10ppm of chlorine added with Trichlor tabs you'll raise the CYA by 6ppm.

Here's good read:

Do You Really Need All These Chemicals For A Pool Or Are They Just Trying To Get Your Money?

Let me know how it turns out for you


Comment By Mark
Date: June 10, 2012

With the 2006 tester, how high does the cl read? Does it go up to 5ppm or higher? How do you deal with water that has one measure that out of wack?

For my water, the pool store said:
CL 2ppm (fcl the same)
CH 150
CYA 20ppm
TA 80
Ph; 7.0
Phosphate: 300

They are suggesting 6+lbs of soda ash (I have 35k gallons)

The water is cloudy, like can't see 3 feet cloudy, I just got rid of the green by super chlorineating it for 36 hours.

What do you think?

Comment By Robert
Date: June 10, 2012

Thanks for the follow up

You can use soda ash to increase the pH of the pool. 1.5lbs. per 10,000 gallons to increase pH 0.2. Using 6lbs. of soda ash at one time might overshoot the mark. I'd start with about 4.5 lbs, wait 8 - 10 hours of filtration, then retest. Don't test too soon. Many say test within an hour or so, but chances are you're not going to get a good reading. It needs to go through the entire system and be returned back to the pool.

You just want to bring the pH up to 7.2 - 7.4 and allow aeration to take care of the rest of the increase. Splashing around and water features such as slides and water falls will burn off the CO2 causing the pH to rise naturally. Remember that pH means "potential hydrogen" and the burning off of the carbon dioxide will cause the pH to rise. This will save a little on chemical use, and save a bit of money as well.

The alkalinity is right on the low-normal side, but nothing worry about. if it dips below 80ppm you can make a small adjustment with baking soda and it'll be fine. The hardness is fine as well.

Pool Alkalinity

Total Alkalinity

The CYA is still a little low. As per the other email, shock with Dichlor until you reach 30 - 35ppm, then go back to chlorine. Optimal range is 30 - 50ppm. It's great the water is cloudy because of the dead algae, but don't get too comfortable. You need to test in the evening, then retest in the morning and see how much chlorine you lost. If it's 5ppm or more, you might still have algae. When you only lose about 1 - 2ppm, you're good. This is where many pool owners fall short. If the pool looks cloudy then the algae is gone, but it might not be. The test is to see how much chlorine has been lost over 8 - 10 hours.

If you're using a Taylor K-2006 kit, you can measure very high chlorine, up to 20, 30, or more. If you're using a yellow OTO kit or strips, they normally only go to 5ppm or so. Red color on the OTO indicates high chlorine, but you don't know how high. That's why I've used the K-2006 kit since 1999, it's the most accurate and you know exactly where everything is.

Don't do anything about the phosphates and don't allow the pool store employees to sell you anything for phosphates. Here's good post about that. Be sure to read the comments on the 2nd page:

High Phosphates Over 1000 & Cloudy Water

Hope this helps and let me know how it turns out for you


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Pool FX

by Alan

I just want to know what's your thought on the Pool FX? It was recommended by a dude from youtube (also a pool guy like you).

So I go ahead and ordered one for my pool. Until I joined the TFP forum. It seems like all the experts are against it. I'm very confused now on should I use it or not?

PS. I'm a new pool owner. Bought this house last August. Trying to learn as much as I can handle. Thank you for all your videos!!

Hi Alan. While I try my best to keep up with new things, I'm not familiar with anything called Pool FX. I know about Pool Rx, but not the product to which you're referring.

I even tried to go on TFP and couldn't find anything about it. TFP is a good forum and you could do much worse than them.

If you could offer a bit more detail perhaps I could give my advice. Thanks.


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