Common Types of Algae | Pond Algae Identification Guide

Common Types of Algae | Pond Algae Identification Guide

Algae, also known as phytoplankton, is present in all ponds and lakes. It’s estimated that between 30,000 and 150,000 different species of algae exist – some so small they can’t be identified without a microscope. 

Algae can appear in a number of different forms, colors, and quantities. Algae serves an important function in every ecosystem, but can become a nuisance when left unattended to. Luckily, there are more than a few treatments when it comes to managing algae growth in your pond or home water feature. 

In this article, we cover the most common types of pond algae and all their identifiable characteristics.  

What are the 3 main types of algae? 

Algae is most commonly identified by color – green, brown, and red. The first step in identifying exactly which species of algae is in your home pond is finding the color category or type in which that algae species belongs. 

Algae can also be identified according to profile characteristics (planktonic, filamentous, or macro algae). 

Green Algae (Chlorophyta) 

Green algae is found in many different water types, including salt water and fresh water. Green algae – an “informal” group as far as science is concerned – uses the process of photosynthesis to convert sunlight into starch, so it can then be consumed as food. 

All green algae has a high concentration of chlorophyll A and B. Both compounds are responsible for giving green algae its “green” color. Depending on concentrations of chlorophyll and other nutrients and minerals in the water, this group of algae can take on a spectrum of green coloration. Within many ponds and lakes green algae takes on the slightly duller, pastel colors of the surrounding natural environment. 

Species within this group can take on planktonic and even microscopic forms, making them easiest to identify during a large algae bloom. On the other hand, green algae can sometimes grow in large mats and clusters throughout the water column. 

Brown Algae (Phaeophyta) 

Brown algae contains fucoxanthin, a pigment not found in red or green algae groups. Phaeophyta is most commonly found in marine environments, and dominates rocky shorelines throughout much of the colder regions. 

The majority of species found in the brown algae group are rooted in the ground. They tend to root down in environments of structure, usually characterized by rocks, shell beds, submerged logs, or even docks. 

The color of brown algae in ponds ranges from a pale beige or tan to yellow-brown and even black. Many of the giant kelp forests we picture bordering coastlines contain species of brown algae. Some of the most common species of brown algae include sargassum, turbinaria, and macrocystis pyrifera. 

Red Algae (Rhodophyta) 

Similar to brown algae, most species within the red algae group can be found in salt water, not fresh water. Although, there are some exceptions. The pigments of phycocyanin and phycoerythrin are responsible for the red coloration. Red algae can be found in colors of dull pink to bright magenta-red. 

Most red algae species are multicellular, and grow attached to rocks, logs, other structures, and even other algae species. Red algae is both abundant and ecologically vital to many environments. They play an especially important role in building tropical reef communities. 

A select few species of red pond algae can sometimes bloom in home aquariums or ponds. It often prefers warmer waters, and can prove devastating to other plants or fish in the water. 

Algae Profile Classification 

As we mentioned before, Algae can also be identified according to profile type. In this regard, algae has three different classifications: filamentous, planktonic, and macro-algae. 

1. Planktonic Algae 

As the name might imply, “planktonic” algae is made up of microscopic organisms, usually taking the form of just one single cell, or a collection of single cells. While each individual organism is naked to the human eye, planktonic algae blooms can be enormous. If left unattended to, they can completely take over an ecosystem, blooming throughout the entire water column. 

Because they are so widespread, planktonic algae are often the culprit of off-colored water in many ponds and lakes. While planktonic algae blooms are usually green, they range in colors of blue to red. Some species even take on a golden hue. 

Because they are free-floating and not anchored to anything in the water, planktonic algae can be pushed throughout the water column by wind or current. They will almost always be found in areas next to the shoreline, where the water is stagnant. 

Planktonic algae blooms can prove devastating to some ponds and lakes. They spread quickly and can deplete other organisms in the water of oxygen and other nutrients. For this reason, planktonic algae can be problematic if you are trying to sustain a healthy fish population. Similarly, algae blooms can sometimes outcompete other plants in the water of oxygen and sunlight. 

2. Filamentous Algae 

The second type of algae classification according to profile is filamentous. You can identify this type of algae by spotting its long, string, fibrous, and slimy form. The body of filamentous algae is made up of long filaments – as the name implies – and takes on a thread-like appearance. 

Similar to planktonic, filamentous algae is composed of single celled organisms that reproduce quickly. These single celled organisms join together to form the long stringy hair-like strands that grow in tight colonies throughout ponds and lakes. 

In many small ponds, these identifiable filamentous algae colonies appear in June or July, and can sometimes cover the entire surface of the water by the end of summer. They culminate in large floating mats, and can sometimes be a disturbance to other organisms in the water, such as fish, frogs, and other plants. 

Filamentous algae has a reputation for growing quickly and even overtaking smaller ecosystems. Small amounts of filamentous algae are not harmful, but you may want to consider an algae management solution before it grows beyond control in your pond or lake. 

3. Macro-algae 

While sometimes found in lakes and ponds, macro-algae is most commonly seen in marine environments. Many of the species of seaweed and kelp found in the ocean are a part of the macro-algae group. 

Because they are a multicellular algae that takes a larger “plantlike” form, they can often be misconstrued as aquatic plants. While they may look similar to other aquatic plants, macro-algae have no true root system and reproduce without flowers. This contrasts starkly to many of the true marine plants, such as certain seagrass species. 

In comparison to many of the other algae types we have covered, macro-algae is often not detrimental to its environment. In many coastal regions – both tropical and temperate – macro-algae plays an essential role in providing habitat for certain fish, crustaceans, and even species of mammals like sea otters. 

Macro-algae can present problems in select environments. Like all algae species, macro-algae can bloom quickly, colonizing large underwater forests. In recent years, this has posed a problem for many of the hard coral species populating ocean reefs. 

Pond Algae vs. Aquatic Plants 

Because many of the different types of algae in ponds can be confused as plants, it can help to do a comparison with pond algae pictures. Before you cleanse your entire pond of the “algae” living within, you may want to cross-reference any present algae with these common pond plants. 


Although it is commonly misidentified as a filamentous or macro-algae, stonewort is actually an aquatic plant that offers many benefits to its ecosystem. It can provide necessary habitat for fish species and the insects they prey on. 

Stonewort also helps to stabilize sediment at the bottom of ponds and helps to add necessary oxygen to the water. Like most species of pond plant, stonewort and its close relatives are beneficial in controlled amounts, but can overtake an environment without close management. 


This small, almost microscopic pond plant is often confused with planktonic and filamentous algae species. It is usually found in shades of light green, and like algae, floats freely in the water without any anchoring root system. 

Similar to planktonic algae, the location of watermeal is subject to wind and water currents, usually collecting in stagnant areas near the shore. Watermeal is most easily identified by its characteristic small, seed-like structure and gritty texture. 


Just the same as watermeal and stonewort, duckweed is an aggressive pond plant that can spread rapidly under the right conditions. Although not microscopic, duckweed is composed of small, single leaf structures that usually grow together in clusters or colonies. 

The free-floating leaves of duckweed grow on top of the water and take on the appearance of a miniature lilipad. It’s most regularly identified by its small leaves and underhanging roots. 

Algae – Friend or Foe to Ponds 

As far as lake or pond maintenance is concerned, pond algae can be both crucial and detrimental to the water system. It provides essential habitat for many of the insects and other foods for small bait fish and fingerlings. 

At the same time, algae blooms can happen rapidly, often outcompeting other organisms in the water for oxygen and essential nutrients. The good news is that there are more than a few suitable fixes when dealing with an algae overgrowth, ranging from oxygenating pond plants to pond cleaner solutions. Proper pond aeration can be a great long term solution!
You can see our products
See Products
Back to blog

Leave a comment

Please note, comments need to be approved before they are published.