Comments for Algaecide Overdose

Average Rating starstarstarstarstar

Click here to add your own comments

Aug 22, 2015
Overdosed the Algecide 40,
by: Kim

Mary I had the mustard algea in my pool and my ph and alkalinity levels were low. Pool store told me to increase the ph and use shock and Algecide. I did all those and I used 1 gallon of Algecide 40 (alkyl demethyl benzoyl ammonium chloride) for my pool which takes 26000 gallon of water. After extreme foaming it cleared itself up and all algea is gone but I realized all the bugs or any living mechanism dies suddenly when it touches the water. I also realized continues foaming when I add water, or when it rains. In the skimmer there is yellowish colored foam and a grease looks like a motor oil. I clean it but it is consistently happening. When I did calculations I realized I used Algecide 8 times more than what I should. Also there is still Algecide smell in the pool. My ph and alkalinity is normal now, chlorine is extremely high and water is clear. I did read i can emphy the pool half way and fill it up again but it is the end of the season and I may use the maybe 5 or 10 more times before I close and cover it up with pool cover. I am not sure whether it is safe to use the pool like this or is it safe to close the pool like this? Is there any other way (besides emptying the pool half way) that you recommend? Or is it better to keep it like this since I will close the pool for winter anyways? I also read it may be safe to get in but it may change the hair colour. I have a dark brown hair, I don't think colour would change or I am ok not to put my head in water If I shouldn't. One other Friend told me keep it in that way, it will be ok over time or if I worry I can increase the ph to decrease the chlorine level. I just don't wanna mess more than what I did. Robert, you were telling shocking would break the Algecide down but my chlorine level so high already, should I shock it to get rid of the overdosed algicide effect? Or should I increase the ph to drop the chlorine and then shock it ? What is your recommendations?
Thank you in advanced.

Hello Kim. Unfortunately there's really not much you can do when too much algaecide is added to the pool. I can assume by your comment that you've read up on this. Yes, maintaining a high FC level, 12 - 14ppm, can help speed up the process. You say the FC is high but I have no idea what that is. It could be 7ppm or 27ppm.

The fastest, safest, and best remedy for an algaecide overdose is diluting the water by doing a partial drain and refill. The algaecide will dissipate over time. This is why you add it to the pool. You can decrease the pH to 7.0 - 7.2 so the FC will be more active and that can help, however, the algaecide will simply need to work its way out if a partial drain and refill is not done.

If you feel your situation is more complex than this, I do phone and/or SKYPE consultations. It makes things go much faster and many people have found it extremely beneficial, saving them time and money in the long run. All your questions will be answered. I have nothing to sell you so you know I'm not bias. If you purchase a personal phone consult you'll get all 3 eBooks for free.

Pool Consultation

Clear Blue Pool eBook

How To Clear Up A Green Pool eBook

Swimming Pool Resources


Jan 05, 2015
Should I Shock After An Overdose Of Algaecide?
by: Mary (Charlestown, Indiana)

I have a yellowish, oily film on top of the water and foam coming out of the filter. The customer service people for HTH told me that I overdosed the above ground pool with algaecide.

I can not financially cope with draining and refilling the pool. They informed me to let it naturally dissipate.

Is it alright to shock the pool now and will it help with the problem or make it worse?

Thanks for the question Mary

Many times the cheaper and less expensive algaecides, also known as Algaecide 40. These are known as linear quats and contain the ingredient "Alkyl dimethylbenzylammonium chloride". This tends to foam.

If you're going to use an algaecide, I always recommend using a PolyQuat 60. This has "Poly{oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride}". Look for this one. With good chemistry you should never need an algaecide, only in a very small amount of cases. Many of the cheaper algaecides use copper and metal fillers in them. Look at the ingredients in the one you used.

Algaecide breaks down but it may take a week or longer. They're added on a weekly basis because they do break down. Shocking with chlorine will speed up the breakdown process.

Foaming can also occur in pools with low calcium hardness. For vinyl pools you can bring the hardness level to 100-150ppm and for plaster pools 150 - 250ppm is recomended.

I'd like to have your complete chemical readings: Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper). There might be something in the numbers that I can look at and see what's going on. Again, an algaecide should only be used for extreme cases such as going on vacation or if you travel and can't test the water twice per week.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.


Click here to add your own comments

Return to Algaecide Overdose.

Return to Pool Algaecide.