How to Tell if Marimo Moss Ball is Dying?

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Marimo moss balls are popular aquarium decorations. The unique shape, velvety texture, and vibrant green color help these ornaments stand out and transform the look of your tank.

Another reason why they’re so popular is that they’re hardy and low-maintenance.

However, even these plants can experience health problems. I’ll discuss this in today’s article. Keep reading to learn more about Marimo ball care requirements, health problems, and symptoms thereof.

This information can be useful if you consider adding a moss ball to your tank.

Can a Marimo Moss Ball Die?

Marimo moss balls are known for their longevity and non-demanding nature. They’re easy to take care of and can live for 200 years or even longer under the right conditions.

However, a Marimo moss ball can die much earlier in an unsuitable environment.

Nutrient deficiencies, poor aquarium parameters, and fungal or algal parasites can all sicken and slowly kill a moss ball.

Luckily, it takes a while for symptoms to progress to this point. If you keep a close eye on your Marimo balls, you’ll notice the signs in time to take action.

There are a few things to watch out for. Changes in shape, color, and texture will let you know when something is off.

Typically, a sick Marimo ball will show the following symptoms:

– Discoloration

Such color changes happen due to nutritional deficiencies or unsuitable parameters. Too much light commonly leads to brown spots, as the Moss ball gets slowly fried. Too little light reduces chlorophyll production, leading to a loss of pigmentation and a discolored appearance.

– Turning Black

Black portions signify active decay, commonly caused by poor water chemistry, fungus, or algae. Such changes require immediate attention. Rot can spread rapidly and deep within the moss ball, so it needs to be treated as soon as possible to save your plants.

– Feeling Slimy or Mushy to the Touch

Naturally, Marimo moss balls have a soft and fuzzy feel, similar to wet velvet. If you notice any changes in texture, that’s a sign that your moss balls are unhealthy. A slimy texture, especially if accompanied by white spots, is often an indication of either fungal or algal infection.

– Shedding

Does your moss ball look green and healthy but falls apart every time you take it out of the water? This might be an early sign of sickness or nutrient deficiencies. It’s a common occurrence in the early stages of an algae attack as well.

– Funky Smell

If you notice any unusual smell when inspecting your moss balls, this is another sign that the Marimo is decaying. Sometimes, the decay may start from the bottom up or the inside out, so you don’t have any visual cues of sickness. But the smell never lies.

Marimo Moss Ball Requirements

Meeting Marimos’ care requirements is one of the best ways to treat and prevent unpleasant symptoms and death.

Establishing a proper maintenance routine and suitable environmental conditions should be your priorities when looking after moss balls.

Let’s take a closer look at what this entails!

– Water Parameters:

Marimo moss balls prefer cooler water, ideally below 77 °F, and a pH between 6.0-8.0 at most. The moss ball will develop brown spots if the water is too warm. A pH that’s too low or too high might lead to texture changes and rot.

Marimo moss balls also prefer brackish water and thrive with a salinity of up to 1.015. Adding aquarium salt is a quick remedy for discoloration.

This shows how important it is to maintain the appropriate water parameters.

– Low Artificial Light Exposure:

Marimo moss balls have low light requirements. But they still need some light exposure to ensure proper photosynthesis.

Medium to high light exposure should be avoided as it can cause brown spots and algae growth. Remember to occasionally rotate the moss balls to ensure light exposure from all angles.

– Periodical Water Changes:

Everybody likes clean water. Aquatic plants are no exception. Maintaining aquarium hygiene prevents harmful bacteria, fungi, and parasitic algae, which could otherwise attack your Marimo balls.

So, changing the water and cleaning the tank regularly is important. If you don’t keep any fish, you should still do a 50% water change twice monthly.

For fish aquariums, you must adapt the cleaning routine to the bioload of your tank.

– Weekly Cleaning:

Moss balls are susceptible to algae growth. Apart from that, sometimes, debris from the water can gunk up and suffocate the plant.

You need to clean your Marimo balls from time to time to prevent these problems.

Cleaning is quite rapid and simple, though. You have to transfer the moss balls to a container filled with dechlorinated water.

Gently squeeze and roll the moss balls with your hand. Rinse away the gunk, and be careful when shaping the moss back into a sphere.

– Friendly Tank Mates

To keep your moss balls in a community aquarium, you must choose the tank mates carefully. Some species can be helpful, while others will outright ravage the moss balls.

Friendly and gentle tankmates include Bettas, Tetras, Rasboras, Swordtails, Dwarf Cichlids, freshwater shrimp, and snails.

These animals are small-sized and plant-safe. Shrimp will nibble on the biofilm that grows on the moss ball, keeping the Marimo vibrant and healthy!  

Sometimes, fish gently nudge and move the moss ball, which is good for even light exposure. It also acts like a shaping force, keeping the moss ball perfectly spherical.

Avoid large, herbivorous, or aggressive species. These will bite, poke, or tear apart the delicate moss balls.

Some examples of no-goes include turtles, axolotls, crayfish, silver dollars, goldfish, mbuna cichlids, plecos, and Oscars.

Marimo Moss Ball Health Problems

We typically only think about health problems when it comes to animals. But even plants can suffer from such ailments. Plant health problems are less diverse and complex, but they still require treatment and close attention.

When it comes to Marimo balls, there are two major health issues to watch out for:

– Nutrient Deficiency

Moss balls are some of the lowest-maintenance aquarium plants. You’ll often see people saying they don’t need any fertilizer or special nutrients. This can be misleading. Moss balls have low nutrient requirements but can still develop deficiencies.

Some nutrients of interest for Marimo balls include CO2, phosphate, nitrates, sodium, chloride, and light (yes, light is a macronutrient for plants!).

Deficiencies can easily occur, especially in fish-free and plant-free aquariums. If you’re keeping your moss balls in a lone bowl and not using fertilizer, you’re doing your plants a major disservice.

Likewise, moss balls can become nutrient deficient in a heavily-planted tank. They don’t have the advantage of roots, so they can’t compete with nutrient-hungry and fast-growing plants.

Common signs of nutrient deficiency in moss balls include discoloration, brown or light spots, darkening of the base color, stunted growth, withering, and shedding.

– Infection

Wait, plants can catch parasites? You bet! Parasitic species of bacteria, fungus, or algae can all wreak havoc on your beautiful moss ornaments.

These organisms grow on the moss, stealing its nutrients and eating it alive. This leads to rot and decay.

Infection is common in fish tanks or tanks containing multiple plant species. This is why you should always quarantine new plants and fish before introducing them into the tank. Poor water parameters can also exacerbate the spread of the infection.

Sings of infection include white fuzz, colored spots (white, brown, red, blue, or black), an unpleasant smell, changes in texture, and the moss ball breaking apart.

If you notice these signs, you must clean and disinfect the plant. Sometimes, you might have to cut off the dead portions of the moss ball.

Why Is My Moss Ball Falling Apart?

Moss balls get and maintain their round shape thanks to their environment. In their natural habitat, moss strands tangle together and form a sphere because of the waves and water currents.

The ball doesn’t get this mechanical force to keep its round shape in an aquarium or bowl. Thus, the strands can loosen up, making the ball fall apart.

If your Marimo ball looks otherwise green and vibrant, it just needs a little bit of help to stay in tip-top shape. You can provide water movement via a filter, a water pump, an air stone, or any combination thereof.

You can also gently squeeze and roll the moss balls back into shape every time you clean them.

This is the best-case scenario. Sometimes, there are other causes for moss balls breaking apart:

– Moss Ball Is Too Large

Moss balls, like other plants, can outgrow their nutrient-storing capacity. A large moss ball might appear dull, misshapen, and loosely strung together.

In that case, some pruning will help the moss strands regain vitality. All you have to do is to section the ball into however many pieces you want, then roll each piece into a new sphere.

– Poor Environmental Conditions

An unhealthy moss ball is likely to shed as a response to stress. Shedding happens when your Marimo balls lack appropriate nutrition or are dealing with poor water quality and infection.

The plant is trying to preserve its energy to stay alive. Thus it lets go of any excess growth it can’t maintain.

Poor environmental conditions include high water temperature, too little or too much light exposure, unhygienic conditions, algae growth, and nutrient deficiency.

Shedding might also accompany other symptoms, such as color and texture changes.

– Herbivorous Fish

Marimo balls are especially enticing for herbivorous fish. That’s because this “moss” ball is actually a type of filamentous green algae called “Aegagropila linnaei.”

Plant-eating fish will go crazy over this plant, biting, grabbing, and pulling on the algae strands.

This not only causes damage; it also loosens up the tangled filaments. Constant attacks from fish will make the moss ball lose its shape and start shedding.

This is why you don’t want herbivorous fish near your Marimo balls.

Why is My Moss Ball Floating?

Is your moss ball constantly floating up to the surface? Don’t worry; this is completely normal and a sign of a healthy Marimo.

This happens when oxygen bubbles get trapped between the tight moss filaments. Since oxygen is lighter than water, the trapped gas in the moss ball must rise to the surface, pulling the moss ball along with it.

Your moss ball produces oxygen during the photosynthesis process. Light exposure allows the plant to create new oxygen, which then gets trapped inside.

This explains why the Marimo typically floats during the day or when the aquarium lights are on.

The solution is quite simple. To release the trapped oxygen, grab and gently squeeze the Marimo underwater.

Once the tiny gas bubbles are out, your moss ball should sink back in place. Or you can just let it be. The oxygen can also dissipate naturally throughout the day.

How to Keep Marimo Moss Ball Healthy?

Marimo moss balls are different from other aquatic plants. As such, they have unique needs.

Keeping a moss ball healthy means a combination of environmental parameters, hygiene maintenance, and even some hands-on intervention.

Here’s what you should do to keep your moss ball in perfect condition:

– Maintain stable mild water temperature

Sometimes, Marimo balls might show health problems even at temperatures above 70°F, but most thrive in water up to 77°F.

You might achieve these values even without an aquarium heater (or chiller). But you’ll have to be mindful of temperature fluctuations throughout the year.

– Create a brackish environment

Marimo Balls thrive in a water salinity up to 1.015 SG. If you don’t keep any fish in the same aquarium, you should ideally use aquarium salt.

You’ll also have to invest in a refractometer. This equipment allows you to monitor the water salinity quickly and effortlessly.

– Keep the water, tank, and moss ball clean

Keeping a clean aquarium is the best way to maintain a healthy, neutral water pH. The first thing you need to maintain clean water is an aquarium filter.

You must also maintain a cleaning routine to prevent algae and fungus infections. Ideally, you should complete twice monthly water changes.

If you have fish, you should also siphon the substrate and wipe the aquarium down during water changes.

The Marimo itself requires a weekly cleaning to remove biofilm and debris gathering on the surface.

– Provide appropriate nutrition

Plants require three things— light, macronutrients, and micronutrients. Marimo moss balls have low nutrition requirements overall. They thrive under low light exposure.

They also generally need no fertilizers. But they can suffer from inadequate nutrient intake under certain conditions (no fish in the tank, no substrate, and too many other plants, to name a few).

I’d say it’s still a good idea to ensure sufficient light exposure and nutrient intake. A little extra nourishment can’t hurt. A liquid fertilizer could help your Marimo ball thrive and grow faster, even if the moss ball is otherwise healthy.

You can find specialized Marimo fertilizers that contain all the nutrients your plants need for easy supplementation.

– Don’t forget shaping and rolling

The moss ball can’t move, so it needs some mechanical help to keep its shape and stay healthy. Without regular reshaping, the moss ball tends to flatten or loosen over time.

One of the things you should do is spend a couple of minutes each week rolling the ball back into shape.

Speaking of rolling, you must also roll the moss ball regularly in the tank. Keeping only one side of the ball facing the light can lead to problems.

The more the bottom of the ball goes without light, the more likely it is for that portion of the moss to rot and die. Remember, the entire ball needs light exposure, not just some parts!

How to Tell if Moss Ball is Dead?

We’ve already gone over the symptoms of a dying moss ball. A dead moss ball will exhibit most of the same signs but all over.

In the case of a dead moss ball, there’s nothing left to prune. A dead moss ball is either completely brown or black. It might be covered in mold or fuzz as well.

There should be no green portions left on the outside or inside. A dead moss ball will give off an unmistakable stench when taken out of the water.

Dead moss balls also won’t hold their shape anymore. Handling will make it fall apart into a handful of mush.


Marimo moss balls are hardy and easy to keep; their 200+ years lifespan proves it. However, even these plants can suffer health issues or die much earlier.

Changes in color, texture, or smell are telling signs of sickness or death.

You can easily avoid such problems by creating a suitable environment and providing proper care.

Remember— Marimo balls thrive in mildly warm water with a neutral pH. They also require a clean environment and regular water changes.

You must clean the moss ball weekly to prevent algae or debris from suffocating the plant. Finally, Marimo balls also need proper nutrition.

This includes low artificial light exposure and, in some cases, a liquid fertilizer.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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