Algaecide - Further Reading

What are Algaecides for Pool Water?

Algaecides are chemicals that may inhibit algae growth in pool water.

Algaecide will not clear an algae problem once you have algae in pool water.

Algaecides do not sanitize the pool water.

In general TFP does not recommend the use of algaecides for regular pool care. If you maintain the proper FC/CYA ratio in your pool water algae will not take hold.

Using algaecide regularly masks the fact that the pool water is not safe to swim. Chlorine serves both as an algaecide and a sanitizer. If you get algae, your chlorine level is too low for swimming because there isn’t enough to prevent the transfer of pathogens. No amount of algaecide will make the water safe even if it keeps the water crystal clear. This is the fundamental reason we don’t recommend regular algaecide use during swimming season.[1]

Algaecides are used as a preventive treatment either at winter closing or specific processes like Ascorbic Acid treatments when the FC level must be low.

For closing a pool when water temperatures is above 60F an algaecide with Polyquat 60 may prevent algae and having a green pool when opening.

What is Polyquat 60?

Polyquat 60 is short for Poly{oxyethylene(dimethyliminio)Ethylene (dimethyliminio)ethylene dichloride}[2] 60% and is a quaternary ammonium cationic polymer.[3]It is a chemical algaecide. Many manufacturers bottle it. Look for pure Polyquat 60 like from Pro Team.

Chlorine will oxidize Polyquat 60.

Polyquat 60 is a mild clarifier. The polyquat turn into a clarifier when broken down.[4]

Polyquat 60 is the sanitizer in optifree contact lens solution so it's also safe for eyes.[5]

Polyquat 30 is a lower concentration of Polyquat.

Polyquat is very stable and is not expected to degrade if sitting on a shelf.

Follow the instructions on the bottle for circulating the water.

Who Makes Polyquat 60?

Buckman Laboratories, in Memphis, TN, makes all the polyquat sold in the US, regardless of the label. Arch(HTH), BioLab (Bioguard, Omni, Pool Time, Aqua Chem, Sun, many others), LaPorte (Robarb, etc.) ALL simply repackage -- and possibly, dilute -- what Buckman makes.[6]

How To Use Polyquat 60 in Pool Winterization?

The following is Buckman Labs (the makers of most PolyQuat products) recommendation on how to use the product for closing a pool:[7]

In our recommended approach for winterization, the pool should be "shocked" with about 5-10 ppm chlorine to destroy any lingering oxidant demand, to remove any residual ammonia or chloramine, etc. After a couple of days, adjust the pH back to 7.2-7.6 and add Polyquat 60 at the maximum rate allowed by the label. This approach allows you to have the maximum benefit from both chemicals. One more point about winterizing: after the addition of Polyquat 60, be sure to keep the circulation pump on for at least 24 hours to make sure that the Polyquat 60 is thoroughly distributed throughout the pool.

If you raise your water to SLAM FC level then let the FC drift down before adding Polyquat 60. Having a moderately higher level (say, half-SLAM level so FC/CYA ratio of 20%) is OK, but the idea is that the Polyquat should last through the winter even if the chlorine does not.[8]

Buckman Labs says that the Polyquat that is broken down is still effective as an algaecide. Moderate to high levels of chlorine break down polyquat, but only turn it into shorter chain polymers that are still effective.[9]

Also, if you close the pool with the water temperature cold (50ºF or below), then the algaecide will last a much longer time even in the presence of chlorine. That's the recommended approach.

Basically, at warm pool temperatures in one week the Polyquat might degrade by at about one-third with normal chlorine levels, but at 50ºF it would take perhaps 5-7 weeks for that same level of degradation to occur. So if you close late enough and open early enough, you could have the algaecide and even the chlorine still have some residual when you open in spring.[10]

Polyquat lasts longer than chlorine especially in sunlight. The main advantage of using Polyquat on closing is that in a pool exposed to any sunlight, the Polyquat will last, especially if the water is cold, so will help to prevent algae growth even if the chlorine level gets to 0. If you cover a pool and close it when cold, then chlorine can last a long time.[11]

How to Use Polyquat 60 in Ascorbic Acid Treatments?

Polyquat 60 needs to be added weekly during the duration of time that you have the chlorine below normal (or at zero during the ascorbic acid treatment). It does not last forever and is not a one-time dose unless you are only having the chlorine be low or zero for less than a week.[12]

Do not mix Jack's Magenta Stuff and Polyquat in a pool. According to the MSDS Jack's Magenta Stuff is acrylic acid copolymer. That's a negatively charged polymer designed to attract and bind to positively charged metal ions. Polyquat is a positively charged polymer. When you mix these two, you form a cloudy precipitated mess. You should never, ever, mix these two together in a pool.[13]

Beware of Algaecide that Contain Unwanted Chemicals or Metals

Many algaecides sold at pool stores contain copper. You do not want copper accumulating in your pool water. The only way to remove copper from pool water is by draining the pool. Copper in pool water can cause staining or turn blonde hair green. For more see Copper in Pool Water.

If you choose to use an algaecide, know what all the chemicals in it are and their effect on your pool water. If you are not sure, ask on the TroubleFreePool Forum before adding it to your pool water.