Why Is Your Marimo Moss Ball Dead (& How To Revive It)

The Marimo Moss ball is a popular pet for many reasons: they’re low-maintenance, cute, and easy to care for. However, there’s one downside to these little balls of green joy, they eventually die. Many people consider the Marimo Moss ball to be a living thing due to its seemingly lifelike movement around the tank in response to changes in sunlight. Just like all living things, moss balls have a life cycle, and eventually, they will die. However, there are ways to prolong their life.

There are also several indicators that your Marimo Moss ball is dying or suffering from health problems. If your Marimo Moss ball has changed color, lost its round shape, or stopped moving altogether, it is likely that it is dying and in need of immediate help. With a little bit of care and understanding, you can keep your moss ball alive and healthy for years to come. Keep reading to know more!

Can My Marimo Moss Balls Die?

Marimo Moss Balls are algae that grow in lakes and rivers in Japan and Northern Europe. In their native waters, they are resistant to rapid deterioration and can live for centuries. But the situation changes when it’s used as an aquarium plant to decorate aquariums and fish tanks.

When compared to other aquarium plants, Marimo Moss Balls don’t need as much care. However, the Marimos in your tank could die if the moss balls are not provided with the basic essentials or if they sustain any other form of physical damage.

Marimo Moss Balls are green, velvety-looking balls. If these moss balls aren’t taken care of properly, they may change color, turning brown, gray, or even white. If your Marimo moss ball turns black, that indicates that it’s dying.

Moss ball isolated on white background

Why Is My Moss Ball Floating?

Moss balls, also called Marimo moss balls, are a strange but beautiful addition to any aquarium. Aquarists like these algae not because they look cute, but because they are easy to take care of and good for the aquarium. If you’re new to Marimo moss balls, you might be wondering why they only float during the day and sink at night. Here are some of the possible reasons:


During the process of photosynthesis, oxygen bubbles are produced by the moss balls. These oxygen bubbles sometimes get caught inside the ball, which helps it float to the top of the water. A ball can lose its buoyancy if its contained air bubble escapes.

It’s the Unique Shape

Marimo balls have a high ratio of surface area to volume, meaning they have a larger surface area relative to their size. This allows them to trap air bubbles within their layers, which makes them buoyant.

It’s Dying

When the algae inside the ball die, the moss ball sinks and loses some of its greenish color. If your moss ball has lost its color and has been floating for a few days, that means it is dead or dying.

Signs Of An Unhealthy Marimo Moss Ball

Marimo moss balls are very resilient and able to survive in a wide variety of environments. They’re edible, adaptable (you can grow them in cold water), destructible, and able to thrive in saltwater. They’re definitely tough.

However, some situations do call for special care and monitoring. There are a number of warning signs that your marimo ball is sick or dying and needs medical attention right away. We’ve compiled a list of the most typical issues that can arise.

Fading to Brown

When the moss ball starts to develop brown blotches on its outside, you know something is wrong with its appearance. It means the ball is in its early stages of death when it is yet salvageable. If the brown spots are just appearing at the ball’s base, it means that the ball is not getting enough sunlight, which is something you’ll want to address. On the other hand, if the ball is beginning to become brown, it may be unclean and in need of a wash.

Coming Out White

The sudden change to white could be perplexing since a decomposing ball is often a darker hue like black or brown. All things in excess are harmful, and if your ball is losing its color and going white, it is dying from too much exposure to sunshine. The marimo ball will dry out and perish if left in direct sunlight, so make sure to relocate it out of the way.

Turning Black

To have the ball turn completely black represents the worst-case scenario. If your marimo moss ball has started to turn black, it means it has started decomposing from the inside out. All of the ball could turn black and be rendered worthless if action is not taken right away. The ball is in its latter stages of deterioration, yet it is not too late to save it.

Starting to Rip Apart

When you take the ball out, it will fall apart, and that’s how you’ll know something’s wrong. Marimo moss balls lose some of their color and vigor even when kept in a tank, making them look less than healthy. When you take it out, you’ll also be able to smell the terrible odor it generated. The good news is that, with regular upkeep, these balls are practically invincible.

Dead Marimo Moss Ball With Awful White Spots

If your moss ball is slimy or slippery, there may be algae growing around it that is taking over. Although algae are the main ingredient in moss balls, other types of algae can be a problem for your marimo because they feed off of your algae. These harmful algae lock themselves around the ball, suffocating it.

What Does A Dead Moss Ball Look Like

Autumn is a great time to take care of your Marimo moss ball. It will not only look better than ever but also be healthier and stronger. But how can you tell if your moss ball is dead? Here are a few ways to tell:

  • If your moss ball has turned brown or black, it is probably dead. Moss balls are green because they have chloroplasts, which are tiny parts of plants that help them make food through photosynthesis. If there are no more chloroplasts, the moss ball won’t be green anymore.
  • It’s time to say goodbye if it feels dry and crumbly. Moss balls that are alive should be firm and wet.
  • Mold or fungus growth. Though a small bit of mold is to be expected, excessive development is a solid sign that your moss ball is no longer alive.

If your marimo moss ball has died, you can try a few things to bring it back to life:

  1. Give it a drink of water.
  2. Put it somewhere cool and dry.
  3. Take it out of the water right away.
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Why Is My Moss Ball Falling Apart?

When it comes to aquarium decor, marimo moss balls are among the most cost-effective options. The problem is that sometimes the moss balls just fall apart. It’s an indicator of rotting health and decay. Even though they are easy to take care of, there are a few things that can make your Marimo moss ball fall apart.

Lack of Movement in the Aquarium’s Water

Lake Akan and Lake Myvatn are where marimo moss balls come from. The water in these two lakes flows in a straight line. Algae take on a spherical form and form moss balls as a result of this. Putting these moss balls in an aquarium with no current could kill them. This could be one reason why the moss balls are falling apart or falling off.

Algae Eat Moss Balls

Algae are what a marimo moss ball is made of. But this can also get hurt by other algae. There may be an increase in nutrient value if the aquarium is not kept clean enough. The increased nitrogen content may cause algae to bloom in the aquarium.

The moss balls can become infested with many different kinds of algae, but black beard algae is among the worst. This is why your moss ball could shed or break apart.

Inadequate Lighting Causes Moss Balls to Rot

Marimo moss ball is one type of plant or algae. Photosynthesis provides all of its dietary needs. Moss balls require adequate lighting in order to perform photosynthesis. Extremely bright light is too much for it to handle. On the other hand, if there’s too much shade, photosynthesis can’t take place. If moss balls don’t get enough food, they might fall apart or shed.

Water’s Inappropriate Temperature

Cooler water is the native habitat of Marimo moss balls. A brownish color may develop in marimos when they are placed in the relatively warmer water of an aquarium. If the water is too warm, Marimo moss balls may break or shed.


Marimo moss balls live longer than any other plant that grows in water. However, it will die too. So, if your marimo moss balls are shedding, it’s possible that their filaments are breaking. This is a sign of the time. Older marimo moss balls don’t stay round for long.

Poor Tank Maintenance

The bioload in your aquarium will rise if you don’t clean it regularly. When filters get clogged, the bioload can suddenly go up. This will help the bacteria that live on the trash and waste to spread. Ammonia and nitrite levels will rise as a result of colonization. That will kill the fish in your aquarium as well as the marimo moss balls.

Herbivorous Fish in an Aquarium

If you have herbivorous fish in your aquarium, they may be causing your marimo moss balls to shed. There are fish species (like plecos) that live at the bottom. It enjoys the algae found in aquariums. Now, if you put a marimo moss ball in front of them, it may tear it up to eat.

How To Keep Marimo Moss Balls Alive

Marimo moss balls are easy to take care of and are a great plant for people who have never grown plants before. Yet, here are some care tips to help your moss balls grow and stay alive for longer.


Marimo balls do not need a lot of light to grow, which is good news. Since marimo quickly turns brown when exposed to too much sunlight, keeping it near a window is not a good idea. The key to keeping them content is avoiding direct sunshine and instead providing them with lots of soft, indirect light.


Due to their aquatic nature, moss balls require a constant supply of chilly water, ideally at a temperature of less than 77 degrees Fahrenheit. The only requirement for this plant species is that the water has to be freshwater.


Water should be changed every two weeks and left out for a day before use to allow the chlorine to dissipate. It’s a good idea to use a brush to remove any algae that may have settled on the container’s surface.

Avoid Fish That Eat Algae

Remember that some animals can hurt your Marimo moss balls. A Marimo moss ball may be damaged by goldfish, crayfish of a certain size, and some species of Plecostomus (Plecos).

How To Revive A Dying Moss Ball

Marimo balls can resist a wide range of temperatures and water conditions, but if the color of the moss ball starts to change, something may be wrong. Here are some signs that your moss ball is dying and what you can do to revive it.

Moss Balls Are Getting Brown or Gray

It’s probably getting dirty if your Marimo is gradually turning a uniform brown or grey. Remove your Marimo from its aquarium and give it a light rinse in dechlorinated tap water or bottled aquarium water. Pick out the brown (dead) sections and add some salt to the water to help the Marimo grow.

Moss Ball Is Changing to White

This indicates that you are providing too much light. Your Marimo will need some shade if you have their tank in a spot where the sun is shining directly on it, so you’ll need to either move the tank or provide some shade. Try turning down the brightness of your aquarium light or switching to a different lamp if it’s just too intense. You can try to shade it with the tank’s plants if it’s in a bright area, or you can transfer it to a tank with lower lighting.

Moss Ball Is Turning Black and Breaking Up

The presence of harmful algae or the inability of fresh water to enter its interior are also factors in this. You may restore the health of your marimo moss ball by carefully unrolling it, removing the dark spots, and rolling it back up again. It will be smaller than before, but it has a good chance of surviving and growing back.

How To Clean Dead Marimo Moss Ball In Tanks

Your marimo moss ball probably doesn’t register on your radar until it turns brown and dies, as is the case with the vast majority of people. Don’t be alarmed! It may and will happen to any one of us. You’re probably here because you have a dead marimo moss ball in your tank and don’t know how to dispose or clean it.

Here are some ways to do it.

  • The dead marimo must be taken out of the aquarium first. You should do your best to minimize any disruption to the other fish in your tank.
  • After removing the marimo, it is time to begin the cleaning process. Putting the marimo in a cup of bleach water and letting it soak for a few hours is the simplest and most efficient technique to do this task.
  • You may also let the marimo sit in the sun for a few days in a bag with some old aquarium gravel if you prefer not to use bleach. This will eliminate any potentially dangerous microorganisms that may be present on the marimo.
  • After it has been exposed to the sun for a few days, you should give it a thorough washing and then wait for it to dry before putting it back in the aquarium.

With these methods, you should end up with a clean and safe marimo that you can put back in your tank without worrying about actually harming your other fish.


Is A Moss Ball Dead If It Floats?

Moss Ball can float to the top of the water when it undergoes photosynthesis and releases oxygen bubbles. That’s just how moss balls are—no need to worry! It shows your pet is in good health.

Is Dead Marimo Moss Ball Bad for Fish Tank?

Rotting and dead Marimo moss balls can lead to dangerously high levels of ammonia and nitrite in a fish tank. These are the most common causes of death in aquarium fish, and no species is safe.

How Do I Know If My Moss Ball Is Dead?

If the moss ball breaks apart and gets entirely black on the inside as well as the outside, then it is considered to be dead. It must be taken out of the fish tank to prevent worse problems.

Do Moss Balls Have Babies?

They propagate asexually through a process called fragmentation, where they divide themselves into smaller segments that grow into new moss balls. So, to propagate moss balls, gently pull them apart into smaller sections and allow them to grow independently.

Does Aquarium Salt Kill Plants?

Even small amounts of aquarium salt can kill plants, so if you plan on adding it to your fish tank make sure you’re removing any plants beforehand. If not the salt will shrink the plants cells from within and cause them to start dying.


All in all, Marimo moss balls are low-maintenance aquatic plants. So if you want to add some life (and oxygen!) to your tank, a Marimo moss ball may be the perfect solution for you. It’s important to remember that marimo moss balls are actually live organisms that need certain TLC. If you’re having trouble keeping your moss ball alive or if it starts to look unhealthy, there are a few things you can do to remedy the situation.  With just a little love and attention, your Marimo will be happy and healthy for years to come!

About the author

Hey! I'm Antonio!

Betta fish keeper for over 6 years now! Since owning a betta I've also housed all kinds of tropical fish, and have seen all manner of problems and how to look after them!

If you need any advice you can always message me or better yet join the Facebook group where a community can answer your questions!