Algae is an informal term for a wide variety of photosynthetic organisms that are not necessarily closely related in the animal kingdom. Many types of pool bacteria are erroneously referred to as “algae”. In the pool industry, it is often attributed to visible “blooms” or colonies of microorganisms growing in a pool.
There are thousands of species of “algae” that may grow in pools. For purposes of pool maintenance, algae tends to be classified according to color: yellow/mustard, green, black, and pink.
In addition, several microorganisms that are referred to as Fungi or Mold can also grow in swimming pools, although they’re much less common than their “Algae” counterparts.
Microorganisms are introduced to pools in a variety of ways; wind, rain runoff, cross contamination of pool equipment, swimmers, etc. Often, multiple species of the above mentioned microorganisms are present in a pool at any one time.
Yellow/Mustard Algae
Yellow or Mustard Algae is a common algae in the sunbelt regions of the United States. It tends to be relatively persistent, and is often found in the shady areas of the pool.
Biology
Yellow or Mustard algae are Xanthophytes (often referred to as “Yellow Green Algae”), part of the Kingdom of Stramenopiles in the Eukaryota Domain. This classifies them in a completely different Kingdom from Green Algae, which is in the Viridiplantae kingdom.
Xanthophytes are Stramenopiles; at some point in their life cycle, Stramenopiles form 2 flagellates (tendril like features) to become mobile; one in particular has tinsel like features on the tendril. The tinsel flagellate acts like a rudder while the other is used for propulsion.
Xanthophytes contain Chlorophyll A and C (but not B) like their closest cousin, brown algae (notably sea kelp). However, they differ in that they do not contain the pigment Fucoxanthin, giving them a much lighter yellow color.
Occurrence in Swimming Pools
Yellow algae tends to prefer the shadiest area of the pool, beginning at the base of a wall and slowly growing upward. It tends to brush off and grow back quickly.
It manifests usually with lower sanitizer levels, typically during hot periods of the year or with increased bather load that increases chlorine burn.
Occasionally, Mustard Algae seems to have become “chlorine resistant”; however, this likely just due to the specific species of Yellow Algae, as some species may be more difficult to eradicate than others. Yellow algae does exhibit the phenomenon towards chlorine as bacteria does to become antibiotic resistant.
Treatment
Yellow algae is relatively easy to eradicate utilizing a combination of algaecides and superchlorination (See: Yellow Treat 2). Prevention is as simple as maintaining proper sanitation levels. In addition, you may consider utilizing a preventative algaecide (see: No Mor Problems).
Yellow Treat 2
Green Algae
Green Algae is most common in humid areas, particularly in North West, South East and Northeast regions of the United States.
Biology
Green algae that is typical in pools can be classified as either Charophyta or Chlorophyta, part of the Viridiplantae kingdom in the Eukaryota domain of life. It is believed that terrestrial plants emerged from Charophyta division.
Green algae can vary widely. Common characteristics is that they contain the primary pigments Chlorophyll A and B (but not C) and utilize flagellates during reproduction (although they don’t have multiple flagellates like Stramenopiles).
Occurrence in Swimming Pools
Green algae can appear in a variety of forms in swimming pools, depending on the specific species of algae. Typically, green algae appears in pools that have extended periods low sanitizer levels They can either grow along walls, in the water, or form “patties” on top of the water.
Typically green algae is not easily brushed off, and is quite smooth or “slimy” to the touch, especially with species that have filament structures.
Common situations where green algae appears are with pool openings, neglected pools, and abandoned pools.
Treatment
Small blooms are relatively easy to eradicate through using an algaecide and superchlorination (see: Green Treat). However, in pools with large blooms, the sheer amount of biomass can require either more superchlorination or a stronger algaecide (see: Swamp Treat).
Prevention is as simple as maintaining proper sanitation levels. In addition, you may consider utilizing a preventative algaecide (see: No Mor Problems).
Swamp Treat
Black Algae
Black algae is less common than Green or Yellow Algae, but can grow in virtually any type of pool across the entire US. Although referred to as “black” it has a very dark blue-green color.
Biology
Black algae is Cyanobacteria, in the Eubacteria kingdom of the Bacteria domain of life. It was once referred to as Blue Green Algae. However, it differs from Eukaryotes in that it has no membrane sheathed organelles, making it not a true algae. It derives its color from the bluish pigment phycocyanin which it utilizes for photosynthesis.
Typically cyanobacteria grow in filamentous colonies. Unlike true algae, they don’t typically have flagellates, but rather the filaments themselves wave for propulsion. Cyanobacteria also typically have very thick gelatinous cell walls, making them more resistant to oxidation.
Some species of Cyanobacteria can produce toxins that are harmful to humans. However, typical colonies in pools are relatively small enough not to pose significant health risk.
Species of Cyanobacteria will form Akinetes in response to changes in environment. An Akinete is a thick walled dormant cell that is extremely durable. When favorable conditions present themselves, these Akinetes will respond to become active cells again.
Cyanobacteria grows in virtually every environment on Earth. It is believed that Cyanobacterial ancestors played key a role in changing the Earth’s atmosphere to be more oxygen-rich during Earth’s earliest periods.
Occurrence in Swimming Pools
Green algae can appear in a variety of forms in swimming pools, depending on the specific species of algae. Typically, green algae appears in pools that have extended periods low sanitizer levels They can either grow along walls, in the water, or form “patties” on top of the water.
Typically green algae is not easily brushed off, and is quite smooth or “slimy” to the touch, especially with species that have filament structures.
Common situations where green algae appears are with pool openings, neglected pools, and abandoned pools.
Treatment
Small blooms are relatively easy to eradicate through using an algaecide and superchlorination (see: Green Treat). However, in pools with large blooms, the sheer amount of biomass can require either more superchlorination or a stronger algaecide (see: Swamp Treat).
Prevention is as simple as maintaining proper sanitation levels. In addition, you may consider utilizing a preventative algaecide (see: No Mor Problems).
Swamp Treat
Pink Algae
Pink Algae is a reddish bacteria growth, sometimes referred to as “Pink Slime”. It is more common in Biguanide treated pools.
Pink Algae is part of the genus Serratia, a type of Proteobacteria in the Enterobacteriaceae family. Enterobacteriaceae is notable for many more familiar types of bacteria like Salmonella and E. Coli. It is a rod shaped bacteria and derives its color from the red pigment Prodigiosin.
Serratia are an opportunistic human pathogen, meaning that it will infect humans under the right conditions. It is believed to account for approximately 2% of hospital related infections.
Occurrence in Swimming Pools
Pink Algae will appear as reddish slime either on surfaces or in the water itself. Often, it will grow around pool fixtures and behind pool lights. It can easily be wiped from surfaces, and appears gelatinous.
It’s more common in Biguanide treated pools, but can occur occasionally in chlorine sanitized pools where sanitizer levels have become or maintained too low. Once established, it can be very hard to eradicate, and grows extremely fast.
Treatment
Exposing as much of the biomass to chemicals in the water is key; this involves scooping out large masses of growth from behind pool lights and fixtures into the pool for treatment. Being a human pathogen, care should be taken to wear gloves – especially if there are exposed wounds on the hands.
Since the larger amount of organic matter will consume more oxidizer, it is recommended you use a medium strength algaecide (See: Pink Treat) and superchlorinate with Sodium Dichlor which has a high percentage of available chlorine.
Swamp Treat
White Water Mold
White Water Mold isn’t very common, but can appear in especially warm climates. It’s not really a mold at all – rather a close cousin of Mustard Algae.
Biology
White water mold is an Oomycete, a type of Stramenopile in the Domain of Eukaryota. Although referred to as a mold, it is more closely related to Yellow Algae, which is also a Stramenopile.
Oomycetes are Stramenopiles; at some point in their life cycle, Stramenopiles form 2 flagellates (tendril-like features) to become mobile; one in particular has tinsel-like features on the tendril. The tinsel flagellate acts like a rudder while the other is used for propulsion.
Occurrence in Swimming Pools
White water mold often appears as tissue paper like debris in the pool water, that breaks apart easily to the touch. It is more common in Biguanide treated pools, but can occur in chlorine sanitized pools where sanitizer has been maintained low for an extended period of time.
Treatment
Although very similar to Yellow or Mustard algae biologically, blooms of White Water Mold tend to be larger. This requires a medium strength algaecide (see: Pink Treat) and superchlorination.
Prevention is as simple as maintaining proper sanitation levels. In addition, you may consider utilizing a preventative algaecide (see: No Mor Problems).
Vinyl Fungus/Plague
Vinyl Plague refers to a phenomenon where a dark stain appears at the bottom of a vinyl liner pool that is the result from a soil fungus. It is often misdiagnosed as metal staining.
Biology
Vinyl Plague is a Fungi, belonging to the Eukaryota domain. Fungi grow in filaments, and contain Chitin (the same compound that forms the shells of crustaceans) in their cell walls. Fungi typically prefer dark, damp environments.
Occurrence in Swimming Pools
The Vinyl Plague is most common with Vinyl liner pools in areas that have high water tables, where soil fungus is abundant. Typically, the ground is left untreated prior to the installation of the Vinyl pool.
Fungus is a unique problem for Vinyl Liners. Due to the nature of Vinyl, Fungi filaments can grow through the liner to reach the water. This manifests as a dark stain at the bottom of the liner that cannot be brushed off, and grows slowly across the surface.
Due to its appearance, it’s often misdiagnosed as metal staining. If the apparent stain is responsive to shocking, or placing a chlorine tablet in its vicinity, it is likely the Vinyl Plague.
Treatment
Since the source of the fungus is the ground soil beneath the liner, the ultimate solution would be to remove the liner and treat the ground with an EPA approved fungicide.
However, it is possible to control the problem through use of high sanitizer levels, and preventative algaecide (see: No Mor Problems). Begin treatment by using a strong algaecide (see: Swamp Treat) and superchlorinating with Trichlor-s-triazinetrione to drive the fungus out of the liner before starting your preventative regimen.
