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I Had the Worst Pool Algae This Spring

The pool algae was the worst on record for me this spring. Living in the northeastern US, we had an extremely warm winter and my pool froze for only about a month. Pools in the northeast will generally freeze from November till March. This year, we were lucky if they froze in January.

I had black algae covering the bottom of my in-ground pool, and the walls were covered in green algae. There were worm tracks all over the bottom of the pool where they were eating the algae. It was a mess and it smelled like the mud at the bottom of a swamp. My pool had never smelled like this.

I started by following my normal routine: I dumped a 32-oz bottle of algae control concentrate, and a few hours later, I super chlorinated the pool and then vacuumed the algae with the pool filter on waste.

My Pool This Spring

I have never experienced a pool this green.  Can you see the black algae?

I have never experienced a pool this green. Can you see the black algae?

It's a very nice green, for a gem, but not for a pool.

It's a very nice green, for a gem, but not for a pool.

I have been maintaining my personal pools for over 20 years, and for the past seven years, I have maintained two pools each year. I open them, close them, and maintain them throughout the summer, and I have never experienced a pool this green. The pump was doing nothing for the green water, and the algae control never even turned the water a different color. Usually it would start killing the algae right away, but not this time.

So I went to a pool expert thinking that maybe other people were experiencing the same phenomenon as I was. He suggested I had metal in the water, so I should remove all the chlorine I just dumped in and add a metal remover. I bought his story and his chemicals, but I was very hesitant. I recommend sticking with your gut feelings as my pool stayed the same color and I was out $35 bucks. The algae was still winning.

Please take a second to vote.

Killing the Pool Algae Fast!

There is hope, there is always hope, and that's why I wrote this article.

I talked to another pool expert at a different store, one where the prices are a bit higher but the advice is priceless. He suggested I dump in 10 gallons of liquid chlorine into the pool, wait an hour, and then use an algae destroyer called Banish. Banish is manufactured by BioGuard, and it will destroy green, black, and mustard algae within 24 hours. At this point I was ready to try anything! So here goes another $76 bucks and a prayer. I just wanted to see a change in watercolor, anything to prove to me that the chemicals are working.

I dumped in the 10 gallons of liquid chlorine and waited about 2 hours, the water was still emerald green and full of algae. I thought, WTF, (Wednesday, Thursday, Friday) that's how many days it's been; I started on Wednesday. It was now dark out, and I turned the pool light on, I dumped in the 32-oz bottle of Banish, and the magic started to happen. The water was turning colors. I let the filter run overnight and I never looked back.

My pool went from dark emerald green to blue in less than 12 hours. It was actually blue and semi-clear, and I could see the bottom on the shallow end but not so much on the deep end. It was blue and the algae was destroyed, yeah baby. I can have my life back! It's very frustrating when you can't see any results. I hadn't seen any type of change in the green water in three days, and I was frustrated to the max.

I couldn't believe that all the chemicals I added to the water didn't change the water color at all. Usually you will see a slight change, but I didn't see any, nada, nothing! That's why I'm sharing my story with you: Banish by BioGuard worked overnight as you can see by the pictures. If I hadn't seen it with my own two eyes, I never would have believed it. I know the liquid chlorine helped in the process, but what changed the water color from green to blue was the Banish. I know because I watched it happen.

My Pool 10 Hours After Using Banish

10 hours after using Banish

10 hours after using Banish

The pool water is clean once more

The pool water is clean once more

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: I have the same problem, and I'm tired of adding chemicals that aren't doing anything. I have an above ground pool of the dimensions 18×33, how much Banish would I need or what would you suggest?

Answer: I recommend two bottles, use one complete bottle as directed, if you need a second dose, you'll have it, if you don't, you can save it for next spring. I guarantee it will make your pool water change color in seconds, not clear, but will change from green to cloudy blue. It will take a few days to clear, then vacuum the pool bottom as much as possible with the filter on waste so you don't filter the dead algae back into the pool. Let me know how you make out.

Question: I have a 39,000 gal pool and have been battling the mustard algae that looks like sand on flat surfaces and slopes of the pool for two months. I have been vigilant every day. I am done with adding high levels of chlorine, brushing, and vacuuming to waste. I have been using 12.5% liquid chlorine. I also have cal-hypo 73% granules on hand. I bought two bottles of Banish. How much chlorine should I add and of which type?

Answer: The Banish should have killed the algae. If you can't kill the algae with chemicals try lowering the PH close to "0" If the PH is extremely low the algae will not have an environment to grow in, you'll need to raise it again once the algae is gone, but it may be the only way to get rid of the algae.


Eddie Carrara (author) from New Hampshire on June 22, 2020:

Hi Steve,

I'm not sure because someone else posted that comment, but I think it has something to do with scaling and liner discoloration that's why there is a chemical called "Metal Remover". I hope HP keeps your link in the comment, it's a nice plug for you, they don't usually allow links in the comments :)

SteveThePoolGuy on June 21, 2020:

Hi I'm a new pool owner looking into getting into the cleaning business so I'm open to any feedback. Why is in the last comment "Please do not recommend products with any copper. Next you will have to use mineral remover chemical turning pool care into an endless cycle. Keep CYA level low and use liquid chlorine and brush, filter, backwash, repeat."

Why is it that you would not be using products with copper? I was just reading something about TDS here:

Does that have a correlation to that count? Again sorry for the noob question but I am looking to learn. Thank you!

Tired of paying others to maintain my pool. on September 19, 2019:

Please do not recommend products with any copper. Next you will have to use mineral remover chemical turning pool care into an endless cycle. Keep CYA level low and use liquid chlorine and brush, filter, backwash, repeat.

Eddie Carrara (author) from New Hampshire on May 13, 2019:

Hi Heather,

Yes, banish is amazing and it works fast. I have moved since I wrote this hub and I really miss my pool lol. Thanks for the feedback Heather I really appreciate you taking the time to comment :)

Heather Ann Gomez from Monterey, CA on May 09, 2019:

It looks like you found yourself a great product! I should tell my mom about it. She lives in Florida, has a pond and a pool. I bet she would be amazed at the results. Your pool looks like a completely different pool afterward. Great hub!

Eddie Carrara (author) from New Hampshire on December 12, 2018:

Hi Samantha,

I'm not sure, can you not buy Banish on Amazon in South Africa? Will not deliver it to you? You could try a concentrated algicide, because that's what Banish is, mixed with a few more ingredients. Let me know, thanks.

Samantha Lockwood on December 12, 2018:

Hi Eddie,

Do you know what the equivalent to Banish is in South Africa?

Eddie Carrara (author) from New Hampshire on June 04, 2018:

Hi Tammy,

I recommend buying 2 bottles and use one complete one as directed on the bottle, if you need a second one you'll have it, if not, you'll have one for next spring. Let me know how your pool looks after you use it, thanks.

Tammy on June 04, 2018:

I have a 18x32 above ground pool, how much banis would i need to use?

Eddie Carrara (author) from New Hampshire on June 16, 2017:

Hi Lorrie,

Do you have any debris at the bottom? If so, remove it first. Did you try vacuuming it with the valve set to waste? This will send any debris out of the pool. Let me know.

Lorrie on June 15, 2017:

On my second round of banish . STill green . Waters is tested by pool store at this point more than once a week . Several hundred bucks later , still green . At my wits end . I've had an pool for 16 years . Worst year ever

Eddie Carrara (author) from New Hampshire on May 31, 2017:

Hi Chris,

My opinion is you Looploc cover is much less work ( no need to pump water off your pool cover) and much safer. Try using Banish to kill the algae now, and also try using a winterizer in the fall, your pool will be crystal clear in the spring and will only need a light vacuum. Let me know how you make out.

Chris on May 30, 2017:

I live in NH and I too have been having this problem - however, I think the problem is my pool cover! I have a Looploc safety cover and it is over 10 years old. The cover mesh is disintegrating and therefore all of the pollen, dust etc. can now seep through the cover! Do people in the northeast still use the solid tarp-like covers? I do not want to spend the $$ on a Looploc!

Eddie Carrara (author) from New Hampshire on May 01, 2017:

Hi Lori

I have never had a saltwater pool so I'm not sure if banish will work in saltwater. If it's really bad, I would at least try banish, it's just an algae destroyer.

Lori Nelson on April 30, 2017:

What do you do if you have a salt water pool and you are having the algae problem?

Michelle on October 02, 2014:

I fought algae all summer too. Wasted tons of money. Thanks for your article. I'm going to purchase and use your method come spring:-)

Eddie Carrara (author) from New Hampshire on May 27, 2014:

Hi Monica,

That's awesome :) The banish will not clear the water but it does get rid of the ugly green color and the swamp look, lol. The blue water gives you hope :) Now that's all you have to do is vacuum and run the filter a few days. I'm glad I could help, and thanks for the feedback, I really appreciate it :)

monica on May 26, 2014:


Wow, just wow! The Banish was took two bottles and 25lbs bioguard shock (nobody around here sells liquid chlorine, they say it's too "unstable")...but the pool is blue...cloudy, but lovely blue! I guess we'll add some salt and start trying to adjust chemicals now...thanks for your help, this is the most helpful advice I have found!

Eddie Carrara (author) from New Hampshire on May 20, 2014:

Hi Monica,

Get the banish!! and about 5 gallons of liquid chlorine, follow the direction on the banish bottle,your water will be cloudy blue within 15 minutes, then it;s just a matter of letting the pool pump do it's job. Once you can see the bottom, then you can vacuum up the debris. Keep me posted on what happens, I'm positive you will be amazed at how quickly your water turns blue :)

Monica on May 20, 2014:

So my pool is blackish- green..ugh! We have shocked it like crazy, and then I ran across your article. ..I'm thinking of ordering the pool opening kit and starting over...or should I just get the banish? Both? I'm desperate. ..

Eddie Carrara (author) from New Hampshire on May 22, 2012:

Hi Tony,

Yes there is copper (metallic) which is derived from copper sulfate in Banish, that's probably why it works so well, no burnt paper tho, probably more user friendly, lol. Thanks for the tip Tony, take care.

Tony Flanigan from East London, South Africa on May 22, 2012:

I'm probably the laziest pool maintainer in the world, and tend to let pool maintenance slide (very badly), especially in winter.

When I want clear blue water, it takes me about 3 man hours, over 3 days. The process is pretty simple.

First I sweep the pool, to get everything into suspension - turns the water a really horrible muck colour. Then I test the water ph levels.

Just after dark, based on the ph I will add the chemicals needed, dump in a kilogram of aluminium sulphate, toss in 4 cap-fulls of chlorine granules, and then switch the pump on, to circulate everything for 4 to 6 hours. I then leave the pool alone for the entire next day, and on the following day I will vacuum the pool manually - this is what takes so much time!

Instead of aluminium sulphate you can use copper sulphate, but prepare yourself for an incredible experience - it turns the suspended dirt in the water into what looks like tons of burnt newspaper. It's extremely painful getting rid off all the "burnt newspaper", but the water is so clear afterward that you can see almost forever...