Algae Will Not Die In My Pool

by Bryce Alexander
(Cherryville, NC )

I have a 20 by 40 pool, 30,000 gallons.

I have shocked the crap out of it and still can not get it to clear up, not even enough to vaccum the alage out.

Is there anything that I am doing wrong?

My pH is 7.4 to 7.6. My alkalinity is 110, and my stabalizer is 30.

I have no metals in the water.

I'm fixing to just put the cover back on it.

I just replaced the sand in the filter as well.

Can't figure this out.

Please help.

Thanks for the question Bryce

Clearing up a green pool does take time a patience, and it's also important in how you do it.

First I would recommend getting a Taylor FAS-DPD K-2006 pool test kit. It the one I've used since 1999 and most pool professional use.

Water Testing Kit

Pool Water Testing

Your chemical readings seem to be fine. pH is good and alkalinity, although just a bit high, doesn't need to be adjusted. It's when you get into range of 130ppm and above should anything really be done about it.

CYA is at 30ppm, which is good for a home pool with a chlorine level between 1.5 - 3.5ppm.

You need to be sure that you're hitting the super chlorination mark, at minimum 10Xs above what you normally run the chlorine. You'll continue to have an algae problem without doing this.

Whenever I've cleared up green pools for customers or even shocked the YMCA pool, I always go for more. When shocking, a little more is better than a little less.

Sometimes I even hit 25ppm for a shock. This is when the chloramines got up there.

What many people do is "shock" the pool, but don't take a chlorine reading afterward. They think they hit the mark, but they don't.

Shock the pool at night and keep the filtration on. This is so the sun and heat won't eat up any chlorine. In the morning you'll have one complete turnover of the pool water.

This is when you'll realize if you hit the shock point. And this is the part that most people fail to do. You may have only hit 8 - 9ppm.

You can't shock the pool, then not test it, or test it after an hour. It needs a complete turnover, regardless of what anyone says. I've personally cleared up hundreds of green pools.

Shock the pool with either liquid or granular chlorine. If you have hard fill water, use liquid.

To get a good shock, 15ppm, you'll need at least 6 gallons of liquid chlorine for a 30,000 gallon pool.

This is the tricky part. When you shock the pool, the algae will consume alot of the chlorine. This might cause the chlorine level to come down. When the algae is dying, it will turn a grayish/white color.

You'll need to manually dose the pool to keep the chlorine level above 10ppm and allow the chlorine to do its job.

If this isn't possible due to time, you can use a PolyQuat 60 algaecide during this process. It will give you a little more time and be a good backup against algae coming back.

Use a large bucket filled with water. Add the chlorine, stir with a stick or PVC pipe, and walk it around the perimeter of the pool. Always add chemicals to water, never water to chemicals.

And be sure you're wearing old clothes, rubber gloves and goggles.

Be sure the sand filter is being backwashed once per day and brush the sides and floor the best you can. This will keep the algae in suspension and it will be filtered out more effectively.

Once you're able, I'd suggest you vacuum to WASTE. This will bypass the filter so it won't get clogged up with more algae. But, keep the water level above the skimmer.

With backwashing, you're going to be using more water than usual, so keep an eye on the water level. 1/3 - 1/2 from the skimmer is recommended.

These are links to my green pool water pages:

Swimming Pool Algae

Green Pool Water

Here's some other links about green pool water. Look these over as well:

Shocked The Pool & Still Having Swimming Pool Algae

Swimming Pool Algae Has Taken Over Our Pool....And Our Lives!

Green Swimming Pool Water In Above Ground Pool..Algae..Shock

Again, this will take time and patience, but you can do it and still have lots of fun this Summer.

Hope this helps and have a fun and safe swimming season.


Click here to read or post comments

Return to Swimming Pool Algae.

Low Alkalinity and pH levels..Still Have A Green Pool..

by Todd
(Pittsburgh, PA)

I recently purchased a house with an inground pool that has not been opened for over a year.

The pool was dark green. I shocked it 4 days ago, but there is still alot of algae on the bottom and the water is very cloudy (cannot see the bottom).

I tested the water with a test strip, and it showed that the pH level was very low, the FC was 0 and the alkalinity was low.

All three categories were at the lowest color.

What should I do?

Thanks for the question Todd

You're on the right track in shocking the pool. That's the only way to kill pool algae and get rid of it.

After a good shock the water should start to turn a grayish/white color. This means the algae is dying out. If this has not happened you'll need to shock it again.

Swimming Pool Algae

Green Pool Water

The reason the chlorine level is showing zero is the algae has consumed all of the chlorine.

The question doesn't say what kind of pool filter you have, but whatever it is, it's very important to keep it cleaned out.

Either backwash with a sand or DE filter once per day or when the pressure gets 8 - 10Psi over your "just backwashed" pressure, or keep the cartridge filters changed out.

Be sure, if you can, to scoop out any debris from the pool; grass, leaves, etc... You want all the chlorine to go to the algae and nothing else.

Use a large leaf rake, not a blue square skimmer.

Get a broom and scrub along the water line to break up any debris.

I would encourage you to get a Taylor FAS-DPD K-2006 pool test kit. It's the best on the market.

Water Testing Kit

Pool Water Testing

Be sure you're hitting break-point chlorination. This is when you bring the chlorine level up 10Xs what is normally run. Without this the pool algae will just sit there.

Here are some links for charts you can use:

Pool Shock

Swimming Pool Chlorine

You'll need to use sodium bicarbonate to raise the pH and alkalinity levels. There are products like soda ash to raise the pH but not the alkalinity too much. Also 20 Mule Team Borax for the pH does the same thing.

If the pH is a little low, don't sweat it too much right now. Chlorine actually works better at a slightly lower pH.

Once the algae is gone, it will be time to adjust the alkalinity. Add your bicarb in the deep end with the pump off.

Allow it to sit for a few hours, then turn the pump back on. You'll need to wait for one complete turnover of the water before you retest. This is usually about 10 - 12 hours.

Pool Alkalinity

Total Alkalinity

Make another adjustment if needed using the same technique.

Raising the pH is just the opposite. Make a slurry with the bicarb or soda ash and broadcast it around the perimeter of the pool with the pump on.

Allow for a complete turnover of the pool water, then retest and make another adjustment if needed.

If you have any water features such as slides, waterfalls, etc... now would be a good time to turn them on. This will help increase the pH level without much happening to the alkalinity.

Swimming Pool pH Levels

Pool pH..Balance & Adjust

You can also go through questions that I've answered in the pool Q&A forum. There's lots of great information and hundreds of questions have been answered.

Swimming Pool Questions and Answers

Remember, this will take patience. Just keep at it and you will have a great pool this Summer.

Good luck and let me know the results.


Click here to post comments

Return to Swimming Pool Algae.

swimming pool care, basic pool care, above ground pool maintenance, inground, salt water

Click Here To Learn How This eBook Can Save You TONS Of Time & Money

Click Here To Learn The Best Way To Clear Up Your Pool 

Recent Articles

  1. White Slimy Film On The Bottom Of Pool

    the water was crystal clear but upon skimming the top we noticed a white slimy film completely covering the pool liner.

    Read More

  2. High Cynaric Acid

    My pool is a 26,000 gallon above ground vinyl liner. around 7/31/2014 the cya raised to 113

    Read More

  3. Can Super Floc Remove Pool Algae?

    Will raising the pH level and adding Superfloc get rid of algae?

    Read More