An algicide is an active substance (pesticide) intended to kill (biocide) or control the development of algae, in particular unicellular algae growing in places frequented by humans or on dwellings.
An algaecide can be used alone or mixed with other components (such as in roof cleaning products (with antifoams and antifungals to kill lichens) or in antifoolings intended to prevent (for a certain period of time) algae, but also shellfish and other marine organisms from growing on boat hulls. Additives or surfactants may be added to the active ingredient.
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Advantages
An algaecide used in a swimming pool is known to allow:
- to use less chlorine for water disinfection, which limits the stinging of the eyes and nose caused by too much chlorine.
- prolong the life of water filtration systems by killing the plants that tend to clog filters and pump inlets.
On roofs, or incorporated in some paints they kill algae that grow on roofs or green up walls.
Disadvantages
Toxicity to the natural environment or even to wildlife
Risk of resistance development, particularly in phytoplankton and cyanobacteria due to their reproductive rate;
Copper, often present in algicides and antifoolings, is toxic at very low doses to many marine organisms and is not degradable.
Some of the diuron (one of the most commonly used algicides) in outdoor murals leaves the paint and pollutes the environment at the base of the wall when it is washed off by rain. It is also found in the air and rain because it is a molecule that has a vapour pressure that makes it very soluble in water and water vapour. The same is true for diuron used in antifoolings. We found worrying quantities of it in the sediments of the Brest harbour. Diuron was one of the pesticides most present in the rains analysed by the Pasteur Institute during 3 years in the North of France (in Lille in particular; in this study, it was much more present in urban areas than in agricultural areas where it is no longer widely used).
The algaecide kills algae, but without removing the cause of their outbreak (which is generally an overabundance of nutrients (nitrates, phosphates, due to fertilizer inputs from runoff water, soil, rain, sewage or duck droppings, etc., or in the case of an overabundance of fish in a closed environment).
In a closed environment, the mortality of a large quantity of algae can be followed by an outbreak of pathogenic bacteria (some cyanophyceae in particular, some species of which can secrete toxins). The mass death of the algae releases nitrogen (some of which will evaporate into the air) and phosphates (which tend to remain available in the water or sediment), which can maintain a cycle of eutrophication, or even dystrophication and anoxia (dead zone, with risk of avian botulism and other intoxications). In an aquarium or pond recently filled with tap water, it is normal for an algal bloom to appear after a few days or weeks. If the water is not too rich in nutrients, it disappears after a few weeks, as a balance is struck between algae, zooplankton and other microorganisms and viruses controlling the algal microflora; the water is said to “vaccinate”.
Types of algicides
There are many algicidal substances, more or less toxic or persistent.
Chemicals
Copper sulphate is an algicide that can be used in swimming pools at concentrations that are not toxic to humans (but toxic to many marine organisms). Copper sulphate has been tested to control the invasive alga Caulerpa taxifolia.
Irgarol, which is more toxic, is one of the biocides used in antifoolings to protect boat hulls.
Natural algicides
Some organisms produce natural algicides to control ecological competitors as part of allelopathic control. The freshwater angiosperm Myriophyllum spicatum (Haloragaceae) emits algicidal and cyanobactericidal polyphenols (prunic acid, catechin…), the most active of which is tellimagrandine II, which inhibits the photosynthesis of cyanobacteria and other phototrophs and inactivates the extracellular enzymes of these organisms by complexation.
The cyanobacteria Scytonema hofmannii (via cyanobacterin) and Fischerella muscicola (via fischerellin A) act in the same way on photosynthesis.
Buy Algaecide Online
HTH 67032 Super Algae Guard Swimming Pool Algaecide Cleanser, 1 qt
- BENEFITS: Kills and prevents all algae types including green, black and mustard algae in your swimming pool so you can enjoy your summertime fun
- USE: Apply directly to the pool for easy DIY pool care
- COMPATIBILITY: Great for vinyl-lined and saltwater pool systems
- FEATURES: Non-foaming algaecide formula destroys algae fast for crystal clear water; Swim 15 minutes after applying algaecide to your pool; Dissolves fast; Won’t fade vinyl pool liners
- INCLUDES: One 1-qt container of Super Algae Guard for your swimming pool water
SeaKlear 90-Day Algae Prevention & Remover, 1 Qt
- Reliable & Effective
- 90-days no algae guarantee (when used according to instructions in balanced pool water)
- Kills and prevents blue-green, green, yellow and black algae
- Non-foaming, non-staining (when used according to instructions in balanced pool water)
- 11.8% Copper Sulfate Pentahydrate; 3% Copper as elemental
- Effective against blue-green, black and mustard algae
API POND ALGAEFIX Algae Control 32-Ounce Bottle, FISHAQUARI (169G)
- Contains one (1) API POND ALGAEFIX Algae Control 32-Ounce Bottle
- Effectively controls green water algae, string and hair algae, blanketweed algae
- Controls green water to keep pond water clean and clear in ornamental ponds and water gardens
- Will not harm fish and plants when used as directed.
- Dose every three days until algae is controlled and then treat weekly
In The Swim Super Pool Algaecide - 1 Quart
- NOTE: WE ARE CURRENTLY UNABLE TO SHIP SUPER ALGAECIDE TO THE STATE OF CALIFORNIA.. We apologize for the inconvenience.
- Provides superior algae-fighting power with long lasting effects
- Safe enough to swim directly after use
- Contains 7.1% Chelated Copper (chelated to protect from staining)
- Non-foaming formula, with no odor
Kem-Tek KTK-50-0006 Pool and Spa 60-Percent Concentrated Algaecide, 1 Quart
- Safe with all pool and filter types
- Helps clarify pool water
- Long lasting algaecide
- Non- foaming algaecide
- For treatment and prevention
EasyCare FounTec Algaecide and Clarifier, 8 oz. Bottle
- Algaecide clears pond and fountain water
- Safe for plants, birds, and wildlife
- NOT safe for fish
- Use in water features, indoors or out
- Keep water free of mosquitos
Pool Mate 1-2150-02 Algaecide 50 Swimming Pool Algaecide, 1-Quart, 2-Pack
- Non-Metallic Algaecide
- For All Pool Types (Vinyl, Fiberglass, Concrete, Gunite, etc.)
- Effective against all algae types (Green, Black, Yellow, Mustard, Pink)
- Prevents and Kills Algae
- Wait a minimum of 15 minutes after use
- Weekly maintenance dose: 2 or 3 oz per 10,000 gallons
EasyCare 2 PACK FounTec Algaecide and Clarifier - 8 oz, Yellow
- Algaecide clears pond and fountain water
- Safe for plants, birds, and wildlife
- NOT safe for fish
- Treats Over 2400 Gallons
- Keeps water crystal Clear
CLOROX Pool&Spa 42128CLX Pool Algaecide
- Prevents and treats pool algae
- Built in clarifier
- Non-foaming formula
- Suitable for all pool types
- Packaging may vary*
Last update 2020-04-15. Price and product availability may change.