Bubble algae (Valonia ventricosa), also known as sailor’s eyeballs or sea grape, are green algae known for their distinctive bubble-like structures. They belong to the genus Valonia, order Cladiphorates, and family Valoniaceae.

The bubble-like structures are spherical and comprise cells packed closely together.

While bubble algae may seem harmless, they can be problematic. They can quickly take over an aquarium, crowding out other marine life and disrupting the ecosystem’s delicate balance. Also, they can harm fish and other creatures, as their thick, bubble-like structures can trap and suffocate them.

If you want to learn more about these algae that can be aesthetically pleasing and a nuisance to aquarium owners, read on.


The surface of the bubble algae is usually smooth, and the color can vary from grass green to dull, brownish-green. Nonetheless, it can appear blackish or silvery in water. The quality of the chloroplasts of the plant determines this variation.

Bubble algae colors can vary from grass green to dark green and, despite their smooth appearance, have a textured surface
Bubble algae colors can vary from grass green to dark green and, despite their smooth appearance, have a textured surface

When viewed up close, these plants have a unique, textured appearance. The individual cells that make up the algae are hexagonal and are packed closely together to form a lattice-like pattern. This pattern gives it a distinctive, honeycomb-like appearance.


Bubble algae appear in tropical and subtropical regions, including the Caribbean, the Gulf of Mexico, the Indian Ocean, and the Pacific Ocean. They can also be found in aquariums and reef tanks. In this place, many consider them a pest species due to their rapid growth and ability to take over an environment quickly.

Bubble algae often attach themselves to rocks, coral reefs, and other hard surfaces
Bubble algae often attach themselves to rocks, coral reefs, and other hard surfaces

In intertidal zones and shallow reef environments, bubble algae are attached to rocks, coral reefs, and other hard surfaces.

Note that Bubble algae can tolerate a range of water conditions. Nonetheless, they tend to thrive in warmer waters with moderate to high levels of nutrients. They can handle a wide range of salinity levels. That’s why they are well-suited to a variety of coastal environments.

In short, bubble algae are a hardy species that can inhabit all oceans worldwide. Also, while they are often considered a nuisance in aquariums and reef tanks, they provide food and habitat for various marine organisms.


Bubble algae’s primary source of nutrition is sunlight. In other words, they contain chlorophyll, a pigment that allows them to convert light energy into organic matter through photosynthesis.

Bubble algae also can absorb nutrients from the surrounding water. They can use dissolved nitrogen, phosphorus compounds, and other trace elements.


Bubble algae primarily reproduce asexually through cell division. A portion of the algae breaks off and develops into a new individual. As you can see, this type of reproduction allows bubble algae to colonize new areas quickly.

Fragmentation typically occurs when the algae are disturbed by physical contact or environmental factors such as storms or strong currents. Once a piece of the algae breaks off, it can grow and form dense mats or clumps.

In the wild, bubble algae reproduce seasonally, with peak reproductive activity occurring in the warmer months. In aquariums and reef tanks, where conditions are more stable and nutrient-rich, bubble algae can reproduce more frequently.

Due to their ability to reproduce and colonize rapidly, it is necessary to take a proactive approach to prevent bubble algae from taking over an aquarium. This idea can include making regular water changes, maintaining proper water chemistry, and avoiding overfeeding. It is also best to remove any bubble algae that do appear as soon as possible.


 Like all living organisms, bubble algae can be affected by various threats. Some of them are:

  1. Pollution: Water pollution can alter the pH of the water, introduce toxins and heavy metals, and reduce the nutrients. It can also cause eutrophication, which is the excessive growth of algae due to an overabundance of nutrients in the water.
  2. Overfishing: Overfishing can disrupt the ecosystem’s natural balance by reducing the number of herbivorous fish that feed on algae. This action can lead to an increase in the growth of bubble algae, which can outcompete other algae species and harm coral reefs.
  3. Climate change: Climate change can cause changes in water temperature, ocean acidity, and sea level.
  4. Physical damage: Physical damage can occur due to human activities such as boating, diving, or fishing. Natural events like storms or hurricanes can prevent it from growing and reproducing.

Facts about Bubble Algae

  • Bubble algae are marine algae found mainly in warm, shallow waters worldwide.
  • They mainly make food through photosynthesis.
  • These algae mainly reproduce asexually through fragmentation, which allows them to quickly colonize new areas and contribute to their rapid growth and spread.
  • Bubble algae can tolerate a wide range of water conditions, but they tend to thrive in warmer waters with moderate to high levels of nutrients.
  • They are commonly attached to rocks, coral, and other hard surfaces in intertidal zones and shallow reef environments.
  • Bubble algae are a fascinating and vital species in marine ecosystems.


What is bubble algae made of?

Bubble algae are large, spherical cells reaching several centimeters in diameter. These cells are filled with a gel-like substance called the cytoplasm, which contains various organelles such as the nucleus, chloroplasts, and mitochondria.
The cell walls of bubble algae are composed of cellulose, a complex carbohydrate that provides structural support and protection to the cells. The cell walls also contain a layer of mucilage, a sticky substance that helps the algae attach to hard surfaces.

Where is bubble algae found?

Bubble algae are found in warm, shallow waters around the world. They are commonly found in tropical and subtropical regions, particularly in the Pacific and Indian Oceans. These plants prefer the intertidal zones, where they are exposed to air and sunlight during low tide. In these areas, bubble algae can be found attached to rocks and other hard surfaces exposed to the atmosphere during low tide. Also, you can find bubble algae in estuaries and mangrove forests.

How do bubble algae reproduce?

Bubble algae reproduce asexually through a process called fragmentation. During fragmentation, a mature bubble algae cell breaks apart into multiple fragments, each capable of growing into a new individual. In addition, bubble algae may also be able to reproduce sexually, although this alternative has not been well-studied.

Who eats bubble algae?

Bubble algae are not a preferred food source for most marine organisms, as their thick, gelatinous cell walls and high salt content makes them difficult to digest. However, some herbivorous species, like sea urchins, feed on bubble algae. Some species, such as the collector urchin and the pencil urchin, have specialized mouthparts that can crush and break apart rigid cell walls.

Is bubble algae an excellent addition to a marine aquarium?

While bubble algae may be visually appealing and exciting, experts hardly recommend them for marine aquariums due to their tendency to overgrow and outcompete other organisms. Their gelatinous texture can clog filters and other equipment, leading to maintenance issues. If you do choose to add bubble algae to your aquarium, it is crucial to monitor their growth and take steps to control populations if necessary.

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