You return from vacation and the pool has turned green, slimy and cloudy. The day after a big, all day party the pool has gone cloudy with that nasty hint of green. Every pool owner knows when algae gets going in the pool. Every pool owner also knows that only an algaecide will kill the pest and let the pool return to pristine condition. So after a quick trip to the pool store or garage you add algaecide and hope for the best. But wait, what IS an algaecide? What are you putting in the water with such high hopes?
Algaecides are chemicals that kill algae as opposed to sanitizers like chlorine that prevent algae and bacteria from getting a foothold in the first place. Algaecides are the last line of defense to prevent draining a pool and starting over. Although the brand names and claims are numerous there are really only two kinds of algaecide available today; metallic and quaternary ammonias. Though both types can be very effective they have different characteristics. Choosing the right algaecide is key to getting the problem solved and swimming again.
Metallic Algaecides Great for winter closing and algae blooms.
The very earliest types of pool algaecide were copper based. Copper is a proven killer and is extremely effective. Copper, either as copper sulfate or elemental copper is suspended in a carrier liquid (water) by a chemical called triethanolamine and added to pool water. Copper concentrations vary from 1 to 7 percent depending on type. Though as effective as any of the newer types of algaecide copper has drawbacks: it can stain pool hardware and turn hair green if chlorine concentrations are too high. It also builds up over time and continued use can stain even a properly balanced pool.
Silver based algaecide is also available. Used to suppress algae and bacteria in electricity-generating fuel cells on space craft, silver algaecide capitalized on use by NASA to win pool customers. Silver algaecide does work but much more slowly than copper. Along with the drawbacks associated with copper algaecides, silver based algae killers are as expensive as, well, silver!
Quaternary Ammonia (Quats) Great for maintenance and algae blooms.
Quaternary ammonia based disinfectants are everywhere; hospitals, nursing homes, restaurants, day care centers and………. swimming pools! Very effective as surface disinfectants at concentrations as low as 2.5 percent, most pool algaecides use a concentration of 30 percent to as high as 60 percent. The main drawback to quaternary ammonia algaecides is foaming. Added to pool water the agitation provided by the pool pump is enough for the algaecide to add nice suds to a pool. Not nice to look at but not a real problem. Quats are relatively inexpensive and a good anytime algaecide if a little foam isn’t a bother.
Polyquats are a refinement of quat algaecides and eliminate the foaming problem entirely. Available in concentrations as high as 60 percent they do the job perfectly but at prices approaching $30 per quart a little foaming might not look so bad. The high price might also be because there is only one U. S. manufacturer!
Low foaming quats are a compromise. Significantly less money than polyquats the foam problem is greatly minimized at a price that makes more sense to many pool owners. Low foam quats are very effective.
-Always add algaecide first. Let it work overnight before shocking. Chlorine will oxidize and destroy the algaecide if added too soon. If the algaecide is metallic staining is an additional reason to wait.
-Check the ingredients. Look for the active ingredients; copper, ammonia etc. Also check the active percentage. If it’s below 30 percent look elsewhere. In particular avoid gallon jugs of algaecide. Generally this bargain stuff has only 5-10 percent active ingredients and will actually cost more to do the same job.
-Spread the algaecide as evenly as possible around the perimeter of the pool. Better distribution means faster action.
-Don’t overdose. More is NOT better especially if using a metallic algaecide.
Rob “Dr. Duck" Coxworth is the driving force behind Webfoot Leisure.com, an on-line retailer of swimming pools, supplies, equipment and accessories. Rob has spent many years in the pool industry in a variety of roles; CEO, manufacturers rep, consultant, National Sales Manager and part time pool float. Dr. Duck likes to write about pool issues and share the information he's gained from working with pool industry firms over the years.