Marimo Moss Ball: CARE, GROWTH RATE, Propagation & More

Moss balls are the perfect aquarium greenery for fish keepers of all levels. They can be used by beginners, who find it easier to maintain them, as well as more experienced aquarists to create aquascape.

In this article, we tried to cover all the important information you need to maintain and even propagate Marimo Moss Ball in your home aquarium.

Overview & Appearance

Marimo Moss Ball is a rare growth form of Aegagropila linnaei green algae which naturally occurs in lakes and rivers across Japan, Australia, and Northern Europe. The word Marimo means “seaweed ball” in Japanese and despite the name, it’s not a type of moss. Marimo algae naturally form in moving water bodies where the water current rolls the algae into a ball shape.

Japanese botanist Takiya Kawakami was the first person to use the term ‘Marimo’ which refers to seaweed ball. This form of algae has been around for centuries and now is a famous aquarium alga.

3 Marimo Moss Ball

For ease of use, the aquarium owners started to use the term “Moss Ball” and that’s the name it became famous for in North America. Moss balls are grown in a sphere shape in their natural environment where water flows slightly fast. This forces the algae to form its famous ball shape.


If you want to remove toxins from your tank and want something your fish can play with, then consider adding Moss Balls. You can place the Marimo ball almost anywhere in the tank. You can even attach them to driftwood, rocks, and decoration or just let them float in the water.

Moss balls usually only reside in smaller aquariums and are typically in front of tanks to show off their unique features.

Moss Ball Care

Moss balls are one of the easiest aquarium “plants” to care for. They don’t need special lighting or feeding and can thrive in most water conditions.

Marimo Moss Ball is naturally found in cold waters in the wild but they can tolerate aquarium temperatures. They can handle high temperatures up to 85 Fahrenheit so this makes them the perfect choice for most aquariums.

They don’t need any special care other than occasional water changes and minimum lighting to thrive. Most aquarists just throw it in the tank and let it do its thing. It does not need CO2 or fertilizer to grow which makes them a great shrimp or betta fish tank choice.

Moss Ball Growth Rate

Marimo moss balls are small and slow-growing plants that grow about 5mm per year. These plants can be found in oceans and lakes around the world.

Altho they come from cold waters in nature, they do well in tank parameters. The ideal tank has an acceptable pH level between 6.5 and 7, and the average temperature is between 65-77 F. Though they grow under varying conditions, they can survive in a range of environments too.


Planting?? No Moss ball does not need to be planted in the substrate. You can drop it directly into the tank and occasionally move them around so it maintains its spherical shape. 

Some aquarists also use moss balls to create miniature trees in aquariums by opening the moss up and pasting it on driftwood.


Propagating is easy and anyone can do it by cutting or splitting the ball into smaller pieces and re-forming each cutting into a ball to shape.

When propagating a Marimo ball, it’s important to make sure you have a very sharp knife or blade. Cut the plant into smaller pieces then roll each into a ball and squeeze hard so that they can maintain their shape and grow in your tank.

New cuttings that don’t hold the ball shape can be wrapped with sewing thread or a fishing line. In time they will grow and will hold their shape.

Maintenance: Yellowish, falling apart, dull color

Marimo moss balls can pick up on debris & detritus so you will need to rinse them off from time to time.

Sometimes Marimo balls can go bad on the inside which you can notice from foul smell or discoloration. If you see these signs, gently remove the plant from your aquarium and cut the part that is gone bad. Reshape it back into a ball and place it back in your aquarium.

The reason for the discoloration or break-up might be related to your water parameters or because they didn’t get enough movement. You should do a few small water changes each month instead of one large change and each time roll your plant around.

One more thing that people should monitor is their tank’s temperature. If you keep them with fish that need warmer water, it is important to remove the moss ball every once in a while and place it in cold water for a few days. Some even keep their Moss Ball in a water jar in the fridge for a few days.

Using cooler water can help them to preserve their firmness and make them live longer.

Moss Ball And Tank Mates

The majority of fish and aquatic plants are often safe to keep with moss balls, even the algae eaters. Moss balls are often the first choice of algae in betta and shrimp tanks.

Bettas and Marimo can thrive in their self-sustaining jar and shrimp will keep cleaning biofilm developed on the moss. It also provides a resting space for betta while keeping the water clean.

We’ve kept Marimo Moss Balls and algae-eating fish together for a long time without any issues. They lived peacefully with our algae-eating fish, such as bristlenose catfish and Oto Cats.

Goldfish and axolotls are also good tank mates for Moss Balls because they both prefer cool water. Goldfish can even toss the ball around which is good for the moss, and your pet fish will have something to play with as well.

Buying A Moss Ball Plant

You can find moss balls just about anywhere, at big retail stores like PetSmart and even smaller local fish stores. When buying your Moss Ball keep the points below to pick the best and healthiest.

The color is the most important factor to consider when purchasing moss balls. In general, darker lush green ones are good quality and should be chosen.

It’s important to keep an eye on the shape of the moss ball as well, they should be round and spherical. If you see a ball that is dull and faded, that’s a clear sign it is dying and you should give it a pass. Moss balls, on the other hand, can have small brown or yellowish spots which can easily be cut off to help the plant live.

If you’re able to handle the plant before buying, it should not smell anything but algae. If the plant smells bad, it might be dying or have parts that are beginning to rot.

Most stores will sell medium size Moss balls, since they grow super slow it’s best to buy the biggest moss ball available in the store. 

Problems with marimo moss balls

The most common problem Marimos have is that they might turn brown when they are unhappy with their environment. If water has ammonia spikes, unfavorable temperature, or imbalanced light then your moss ball might turn brown and eventually die.

To solve this you should perform more frequent water changes and use a stable heat source to keep the aquarium temperature constant. They prefer cool water, if you have your aquarium at high temperatures for fish like discus or German blue rams then we recommend moving the ball to another aquarium. 

High light might also cause this issue, this problem is easily solved by moving the ball to a section where light levels are low.

Frequently asked questions about moss balls

Why do moss balls keep floating?

Marimo Moss Ball are often seen to float when they are first put inside a container and then end up sinking to the bottom after several days. This can happen because air bubbles form inside the Marimo and make it temporarily buoyant. 

To get rid of trapped air, you can gently squeeze the Marimo and put it back into its tank.

Can a marimo moss ball survive outside of water?

Marimo is an aquatic alga, it can’t live out of water for long periods. When left out of the water, they will die once humidity evaporates. To keep them alive without water, put them in a sealed container with some water to maintain the humidity levels. In a sealed humid container they can survive for a few days. 

3 Marimo Moss Ball


Moss balls have become a popular addition to shrimps and betta tanks that both beginners and experienced aquarists use them. These small, spherical-shaped algae are available at virtually any aquarium store and come in a variety of sizes to fit any tank size. They grow slowly and do not spread throughout the tank which makes them the best choice of algae for the tank.

We hope you have enjoyed reading about Moss Ball and use the information in this article to care for this aquarium algae.