Algaecide is probably one of the most misunderstood pool chemicals out there. A lot of people hear “Algaecide” and they’ll immediately assume that it’s something that’s used to treat your pool once algae has already bloomed and your pool has already turned green! Well, this is only partly correct. Algaecide works on algae whether they’ve already bloomed or not (invisible/early stages) and as we always say, prevention is better than cure!

“They’re all the same” is the thing that we hear a lot. Again, while partially true, is a misnomer because while it may be true that all algaecide fight and kill algae, they’re not made out of the same ingredients, and knowing what your algaecide is made out of can go a long way in choosing the right one for your pool.

These are the most common form of algaecide that we can see. For thousands of years (or at least for as long as people have been treating water for drinking and bathing) copper has been the metal of choice. How this works is that the positively charged copper ions attach themselves to the cell walls of algae and poisons the algae from the inside, effectively killing them.

Copper-based algaecides are fairly cheap and widely available from many online pool shops and your local pool stores. The main downside we can see from the overuse and abuse of copper-based algaecide is if you’re in an area with hard water or water that contains a high level of metals. Adding a lot of copper-based algaecides can actually give your water a greenish-tint that can be mistaken for algae and may need some specialized chemical or chelating agent to treat.  

The secret to properly using copper-based algaecide to prevent staining is to follow the directions on the packaging and not go overboard with the application.

On the other side of the scale, we have polymer pool algaecides or poly-quat algaecides. While these are markedly more expensive than other types of algaecides, polymer pool algaecides have been known to be extremely effective in treating algae and as a bonus, they don’t “foam” up your pool water and don’t cause the staining that can possibly occur from the use of copper-based algaecides.

If cost isn’t an issue then polymer pool algaecides are the best types of algaecide that you can use for your pool. But if you’re the frugal pool owner type, we suggest that you only pick up polymer pool algaecides to treat really heavy algae blooms and use other types of algaecides for preventative use. 

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Yeah, yeah, the name sounds silly, but quat pool algaecides or algaecides that use Quaternary Ammonium compounds sits somewhere in the middle-tier of pool algaecide when it comes to cost vs benefit. They’re great for winter pool maintenance and treating algae blooms. The way quat pool algaecides work is that they disintegrate the protective cell layer on algae so that your pool chlorine can easily kill off the algae’s nucleus. So it’s important to ensure that our pool chlorine levels are also on par when we’re using quat pool algaecide. It’s also very important to note that many pool chemical manufacturers like Zodiac manufacture both copper-based pool algaecides and quat pool algaecides and it’s good to check the label to see which one you’re getting. For Zodiac, their quat pool algaecide is simply labeled as “Algaecide” while their copper-based algaecide is labeled as “Long-life Algaecide”.

As you can see from their descriptions, different algaecide types will require different dosing guidelines. Here’s a quick overview of how each algaecide type should be used and how often.

• Copper-Based Algaecide - Copper-based algaecide like the Zodiac Long-Life Algaecide needs only to be added to the pool once a month to maintain adequate algae protection on top of your pool sanitising regimen.
• Polymer Pool Algaecide - This type of algaecide needs to be renewed every two weeks to remain effective as algae preventative in your pool. Couple that with its high cost makes it a high-ticket item as far as maintenance goes.
• Quat Pool Algaecide - Quat pool algaecides are some of the cheapest types of algaecides out there but they don’t last long in your pool. Depending on the concentration of the quat pool algaecide, you may want to apply it once a week or once every two weeks.

READ MORE: Ultimate Guide to Pool Algae

To get the best value for your money, here are some things to remember when adding algaecide to your pool. We must remember that it’s not a magic solution that we can drop into our pool and solve our algae problems then and there.

• Always follow the dosing instructions - The instructions are there for a reason! Read through the label or the instruction leaflet that comes with your algaecide.
• Clean the pool before applying algaecide - Give your algaecide a boost by cleaning the pool of any visible debris before applying. Cleaning the pool beforehand will greatly increase the effectiveness of your algaecide! Leaves and other debris will be attacked by the algaecide which will take the focus away from its desired purpose, which is to deal with algae.
• Circulation is Key - Algaecide work best when they’re moving around your pool so make sure to keep your circulation system active immediately after applying algaecide.
• Pool Chemical Balance - High pH, alkalinity, and both low and high chlorine levels can make your algaecide less effective, so ensure that your pool chemical levels on point before adding algaecide.
• Don’t shock your algaecide - Shocking your pool will absolutely destroy your algaecide. If you’re using copper-based algaecide, then wait until the chlorine levels have subsided before adding your algaecide or wait a day or two after adding your algaecide before shocking your pool, if you don’t follow this then you’re in for a green surprise!

While algae usually stay dormant especially in colder temperatures, we have to take into account temperature fluctuations. Unusually warm winter days can give a window for algae to grow. Having algaecide in your pool can prevent that window from opening by killing algae even while they’re at their dormant phase.

If you’re not comfortable using algaecide on your then you can use Sodium Bromide in tandem with your pool shock. What sodium bromide does is that it reacts with your pool shock and turns into hypobromous acid, which takes care of algae the way the terminator does and absolutely destroys them. Do we recommend using sodium bromide? Yes, and no. It’s absolutely great for when you’re dealing with out-of-control cases of algae where you have a green, swampy pool. But for longer-term use and as an algae preventative, we’ll still go with the long-life algaecide from Zodiac.

While algaecides are designed to kill algae, there will be times where they can get overwhelmed due to a bunch of factors like random increases in temperature, chlorine levels dropping, algae spores deposited by debris, and a lot more. Give your algaecide a boost by dosing your pool with some Zodiac Phosphate remover by starving out algae at the same time!

Algae is a year-round problem and it doesn’t take a break during winter even if your pool does! Algaecide works for you, preventing algae from taking advantage of the break so that when you open the pool in spring, it will still be crystal clear and no surprises (swapy pool!) will be waiting for you. And don't forget some phosphate remover to give your algaecide a boost!