Marimo Moss Ball Buyer’s & Care Guide

Welcome to Marimo Moss Ball Central!

Marimo moss balls make beautiful decorations for fish tanks.

Marimo moss balls make beautiful decorations for fish tanks.

Last updated: 3/1/18. We keep this guide up to date so you get the most accurate information on the web.

(Found something inaccurate? Please let us know ASAP!)

Our site is dedicated to the care and knowledge of marimo moss balls. We are two long-time owners of moss balls and fish-keeping hobbyists, as well as aquarium geeks since College. When we were in college, we would sneak small nano aquariums into our dorm room and the marimos would often be the centerpiece of attraction when we would have “approved” guests over. People often ask questions like the following:

“What’s that green ball thing?”

“What’s that floating egg?”

“What is that thing?”

Even after college, we’re still big fish-keeping fans. I use marimo balls as a decorative item in many of my tanks. I have many aquariums dedicated to just moss balls and nothing else. We made this site because a lot of people seem to be asking questions about them, and are often misinformed.

We hope to clear up some of that confusion and answer your questions to keeping a healthy and happy moss ball. Most of the information here is based on our own experiences and lessons learned. This guide will save you a lot of headaches and confusion. Seriously.

The History of Marimos

marimo moss ball

Marimos are found at the bottom of shallow lakes.

Marimo moss balls originated in Japan. They were found to grow in shallow lakes. They’re popularly found in cold waters, such as their “home” lake- Lake Akan in Japan.

However, they’re also found native in Iceland and Estonia. They grow in shallow bodies on the lake floor up to depths of 2.5 meters. The circular shape, or should we say spherical shape, is caused by the water currents rolling, molding, and forming the ball.

The ball itself is actually made out of algae and that’s been rolled around in circles and formed into these moss balls. Most people know about these little green fuzzy balls simply as moss balls, and you’ve probably seen them in aquariums and fish tanks. They’re not exactly made of moss, as most people would assume.

Marimos are actually a type of algae that grows in partial light and eventually forms into a spherical ball under specific conditions. They are extremely popular in Japan, and now they’ve slowly gained popularity over here in the United States. They’re used in fish tanks, aquariums, display thanks, or even as low maintenance pets.

They require very little special care and offer an interesting experience. They have a spherical shape and are slightly bouncy. They can be kept in a variety of different habitats, including a bowl, vase, or fish tank. Some have had success with terrariums (water-less) tanks.

If you’re looking to purchase a moss ball, definitely do your research before you buy one. Marimos, in general, don’t have many requirements when it comes to care and habitat, but there are a few things you should take into account so you can ensure the health of your moss ball.

Choose the Proper Environment for your Moss Ball

Provide a proper housing environment. Don’t keep your marimo in direct sunlight. Although we mentioned earlier that they grow in sunlight, that doesn’t mean leave them in the sun all day. Algae naturally need light to grow, but a photocycle.

Leaving your Marimo in the sun for periods of time may actually have the exact opposite adverse effect and stunt its growth. In Japan, they actually appear on the bottom of lakes where it’s obviously dark.

Sunrays do reach the bottom, but it’s definitely partial sunlight and you should try to create the same effect environment within your marimo’s habitat.

Remember, it’s a living organism and responds to environmental cues. We suggest you do your research and also choose a place in your home before you actually make the purchase.

Marimo Balls with Other Fish, Shrimp, or Crayfish

marimo moss ball betta

Marimo moss balls are compatible with Betta fish.

If you plan to keep your moss balls in a habitat with other inverts or inhabitants, like crayfish or ghost shrimp, you need to take special precautions. These little creatures naturally love to eat, hide, and forage marimos.

You need to watch out for their habits and make sure they don’t cause too much of a disturbance for your moss balls. They will feed on them, but as long as there doesn’t appear to be any shrinkage of the moss, it’s fine. You may also want to house fish along with your moss balls. It really depends on the type of fish you want to co-inhabit with.

Goldfish are usually a popular choice, however, they don’t make a good tank mate for a moss ball because they love to eat algae. Pleco fish also have the same problem. If you want to house your algae ball with a fish, you should go for a non-aggressive fish that doesn’t need to be housed in schools, such as a Betta fish.

The variety of patterns a Betta fish has can easily match or contrast with the yellow-green or dark-green coloration of moss ball. Betta fish also make great tank-mates because they don’t generally feed on algae, so they will coexist with planted tanks, moss balls, or other aquarium decorations you may have in your fish tank. We definitely recommend that you choose a non-aggressive fish species if you must have fish within the same tank.

Marimos and Saltwater Tanks

That covers freshwater tanks, however many you probably want to keep marimo moss balls in saltwater tanks. This actually can be done, believe it or not. However, it depends on the type of water. Brackish water is a proper housing environment and marimo moss balls thrive in waters with salinity up to about 1.015.

That’s about low-to-mid brackish water. In fact, adding salt to your aquarium is a recommended solution when your marimo moss ball is morphing to a brown shade. They actually do grow in salty water conditions in Japan. In fact, the thickest marimos were found to be where dense salty water from multiple natural springs runs together to join into a lake.

Right at the opening where these springs ran into the lake, the largest algae concentrations within a moss ball were found. That’s because these springs bring in nutrients and salt from runoff sources on the land and bring it straight into the lake.

So, if you want to use your moss ball in a saltwater tank, it’s perfectly fine to do so. Just make sure to check the salinity level and make sure it’s not too high. If you have a freshwater tank and you now want to convert to a saltwater tank, make sure that all the inhabitants in the tank can handle the additional salinity.

Generally, freshwater and saltwater tanks don’t mix. If you have freshwater fish in freshwater habitats, you don’t add saltwater. However, if you are housing the marimo by itself along with some other plants or inhabitants where salt content doesn’t affect them, you may add a few doses of salt and bring up the salinity to grow bigger moss balls.

We suggest using a salinity meter (also known as a hydrometer), which is readily available at any pet store, to make sure you are within the proper range for optimal care of your last ball. We use one made by Instant Ocean that you can check out on Amazon here.

The reason for this is because we also use their sea salt (as you’ll see next), so it makes sense to get them both from the same brand (for calibration purposes).

Some readers have contacted us about what exact salt we use and in what dose. We have a lot of marimos to care for, so we buy Instant Ocean Reef Crystals salt in bulk. It’s available for 10-gallon mixes up to 200-gallons. You can check it out on Amazon here.

It’s used for marine aquariums and is safe for marimos in small doses. Depending on the housing conditions of the ball and other inhabitants, we alter the amount of salt used.

Each marimo that’s housed by itself or with other marimos (that means no other fish or inverts) has a pinch salt added (like a literal pinch). We try to get the salinity to just around 1.010-10.020sg and leave it there. If the ball starts losing color, lower the salinity by doing a water change (partial) or adding distilled water. If you can add salt and the ball doesn’t turn greener, that’s the sweet spot for faster growth speeds.

Change the Water

Slight browning means you need to clean your marimo.

Slight browning means you need to clean your marimo.

Make sure you change the water. As with any fish, you should already know to do partial water changes about once a week or full water changes about once a month. When you do these changes you’re supposed to clean out the tank and remove either a portion or all of the water, depending on if it’s a partial or full change.

The new water that’s added to replace the removed water should be treated with a liquid chlorinator and water purifier. Please read up on how to do water changes if you are new to this or if any of this sounds unfamiliar to you. Getting back to my marimos, whether you keep it in a tank by itself or with other inhabitants, water changes are always important.

We recommend doing partial water changes, removing and replacing about 25% of the water, at least once a week. If you are using tap water, make sure you treat it using a water treatment solution which is available at any commercial pet store.

Although there are reports that you may use regular tap water, different cities and states have different water hardness.It’s much easier to just buy a tap water treatment solution and treat your tap water and use that as prepared water for your partial water change.

However, if you know you live in an area where the water hardness is very low, You may wish to use tap water and that should be fine. This is only if you just have a marimo by itself. But if you have fish, you must use a water purifier. A marimo by itself can be treated with tap water just fine, assuming you have low water hardness, but fish will always need treated water.

Cleaning your Marimo

Marimos require cleaning. You should dive in with your hand and pick up your moss ball every other week and gently inspect it to make sure it’s still clean. I think of it like a dog.

They both need cleaning over time depending on how the tank conditions are. If your moss balls are housed by themselves, they won’t dirty too often. However, if you have other inhabitants in the tank and they leave waste, eating food, or dug up sand, you’ll need to inspect your moss balls more often. When you do the inspection simply pick it up and inspect all sides of it. You’ll instantly know if it’s dirty because it’ll turn brown or gray.

Washing it is easy. Simply squish it multiple times in a container with some clean water. You can also swish it back and forth within the same container, but make sure you have a firm grip on it or else you may break it apart. Afterward, or if you did happen to break it, you can roll it in your palms and sort of mold it into a spherical shape again. Gently roll it around to prevent it from falling apart, but be sure to do this very gently. This will restore the round shape and help the algae strands latch onto each other for a firmer ball.

You’d be surprised to know that in nature, marimo moss balls get rolled around naturally. By sitting at the bottom of the lake, the water current actually helps push them and roll them along the bottom of the lake bed. So, that’s how they keep a rounded shape and structural integrity to stay nice and firm.

Of course, this doesn’t happen in your fish tank so you’ll have to act as a water current and roll them up with their hands. Just be gentle and careful. If you happen to break off a piece and it doesn’t look like it can be reattached you can roll that one up as a separate entity by itself. We think this is a pretty interesting phenomenon and only adds Zen-like qualities to these creatures.

Watch the Temperature – Keep it Cold

Keep the water cold.

Keep the water as cold as possible. It mimics their natural environment.

Keep an eye on the temperature. Marimos prefer colder temperatures. In the wild, marimos only appear in cold waters around Iceland in Northern Japan. If you have an aquarium heater or live in an area where it’s naturally hot, you may have to either get an aquarium chiller or move the marimo’s tank to a cooler area.

If you have other fish in the tank that require a certain temperature that’s warmer, it may not be a good idea to have them with the balls since they have different temperature requirements. However, if you’re housing the ball by itself, it should be fine to simply move the habitat and a cooler spot. It’s actually advisable to place the entire habitat in your refrigerator, assuming it fits, during the hotter months. The temperature that you need to watch out for is 25 degrees Celsius.

Try to keep the temperature between 17 – 23 degrees Celsius. If the temperature goes higher, you have to move it to a cooler area. If you are housing it by itself, you can also add some ice cubes to the water to cool it down if it’s just a temporary hot day. If you live in an area where it’s consoling hot, chances are you’re running the air conditioning. Consider placing the habitat near and air conditioning outlet vent where there will be a constant supply of cool air hitting the tank.

This is why it’s important to do your research in the very beginning and see if you are going to have the right setup and to decide hosing marimos by themselves or with other inhabitants. They all need to have the same temperature compatibility, so that’s why you need to look out for these important considerations.

How to Care for Marimo Moss Balls

Roll your balls. You need to roll your moss ball every other week or so to make sure all sides of it receive light evenly. If you only allow one side to receive that the other side won’t grow and will probably start turning brown. If this happens to you, simply move it so that all sides of the sphere receive some degree of light.

We suggest that you don’t place other moss balls close to it or other decorations in the tank because they may disturb the sunlight that one ball may receive. If that light is coming from directly above, then you can place as many marimos next to each other as you desire.

However, if the light is coming in at an angle, one ball may block the sunlight from being received onto another one. Just be wary of each moss balls’ surroundings and what direction the light is coming from. It’s vital that you try to make sure each ball receives light from all directions and equal an ounce of it at that.

Is your Marimo turning Brown, Gray, White, or Black?

Marimo moss balls are easy to care for and low-maintenance.

Marimo moss balls are easy to care for and low-maintenance.

Keep your marimo healthy.

They’re generally pretty hardy and can withstand a range of temperatures, water conditions, and inhabitants. They can be fed on, they can be grown in cold water, they can be torn apart, and they can be grown in saltwater. They are definitely tough.

However, there are some conditions that require attention and care. You’ll notice this when your marimo turns to a different color.

My marimo is turning brown/gray:

When they change colors to a brown or grayish color, they often need to be cleaned. If your moss balls turns gray or brown, it’s fine- it’s nothing to worry about. Simply give your marimo a nice shower and it should be fine, use the instructions above to clean your moss ball.

My marimo is turning white, or has a white layer:

If it turns white or has a whitish tent, you may have a problem. It probably means that there’s too much sunlight. Move your moss ball to a darker location.

My marimo feels slippery or slimy:

If your moss ball is slimy or slippery, there may be a type of invading algae growing around it. Although moss balls themselves are made of algae, there are foreign invading algae that like to feed on your marimo’s algae. These “bad” algae basically form a seal around the ball and choke it. The solution is to simply wash off the outer layer slowly, and often.

If the layer is visible and easily tangible, use tweezers to pick it off. We suggest you do this early and often until you see no more “bad” algae growth. Increasing the salt concentration of your water may help too. Do both of these tactics and your moss ball with being green and happy again- without the slimy texture.

My marimo is brown even after cleaning it:

If your marimo is brown even after multiple washing attempts, this is a sign that it’s very dirty. We suggest giving it a bath instead of a shower. Clean it thoroughly and swish it around gently in a tub of saltwater. Use a tweezer to remove the browned parts.

My marimo is brown on one side:

If only one side of the Marina has turned brown, it’s because it probably didn’t receive sunlight for a long period of time. Just simply rotate the ball and turn it around with the brown side facing the light. When it becomes green again, simply roll it and roll it often so all sides receive equal lighting.

My marimo broke or I ripped it apart by accident:

If your moss ball is falling apart, you can pick up the last part and roll it into a ball by itself. Be sure to give it a cleanse and reform it with your palms. Do this for both the original ball and then newly-formed one that you just made. Inspect the color and make sure it doesn’t turn brown. If it does, it needs sunlight. Give all parts equal sunlight and also wash them often. The new ball should turn bright-green after going through a slightly darker-green phase. You’ll now have 2 moss balls from 1.

My marimo is turning black:

If your marimo turns black, it’s probably due to neglect and improper care. It could also be due to hostile algae that hasn’t been treated or it has simply been neglected for too long and regular maintenance hasn’t been practiced. Immediately remove the black parts and wash the ball. Reform it easy multiple times a week until it becomes green again.

If it changes to any other color, refer to this guide and treat it accordingly. Chances are, you are new ball will be much smaller than it was before, but at least it will survive and begin growing again. Be sure to increase the salinity of the tank and watch for color changes. Treat changes immediately using this guide.

How to Choose a Healthy Moss Ball

Your moss ball should be full and green!

Your moss ball should be full and green!

Choosing a healthy marimo can be difficult, depending on where you buy your moss ball. You need to be on the lookout to make sure you’re choosing a healthy and genuine Marimo. Many stores actually carry fake moss balls because they look just like the real thing- whether intentional or not.

So you need to be sure that you choose the right ball. We put together a few pointers to help you choose a real one and a few other points to consider when you’re staring at these moss balls in the tank.

The first thing you should do is to ask the store owner to let you handle it. Feel the shape of the ball by rolling it between your palms. You should be able to easily mold it and shape it into whatever you want. If it’s ovular, you should be able to shape it into a more spherical shape without too much force. If it stays in a non-moldable shape, it’s probably a fake.

You should also be able to pick it apart. The store owner probably won’t let you do this, but you should be able to get a feel for it just by feeling the texture of it. It should feel loose and easily broken apart if you were to attempt it. It should be fragile yet feel like it’s stringy at the same time. A better way to put it would be fragile and firm. We suggest that you ask the store owner before you attempt anything too dangerous.

You should be able to feel the texture of it with your fingers and graze over the moss. It should feel bumpy and crater-like. A real marimo ball has a whole bunch of craters, strength, hard parts, soft parts, and bumps all over the surface. If it’s too smooth or too perfect, it’s probably fake.

You want to find imperfections all over the surface, which is perfect. Imperfect makes perfect. We suggest that you don’t only feel the surface, but also dig in to see what’s below it. It should all be the same material and your fingers should easily penetrate through the surface.

Fake moss balls usually have a plastic ball, such as a ping pong ball, in the center and are covered with fake moss. You may be able to see this by the center simply looking through the moss. If you see any weird colors from within, it’s probably a fake. Of course, this doesn’t work with giant moss balls since the moss will be too dense for you to see to the core of it. However, for mini ones, you may be able to see the center through the cracks.

If your pet store carries balls in plastic packaging or some kind of container, it’s probably a fake. A real moss ball should be kept in a planted tank in a complete setup. But, this is not always the case, as they can be transported and sold in some kind of packaging, including real ones. This is just another thing to look out for.

When you inspect the ball, give it a little squish. You should easily have it conform to the shape of your fingers and you should feel like it can be molded into any shape you desire as if it were modeling clay.

Although we don’t suggest that you do this in front of the store owner, make sure you do it at least a little bit just to get a feel for it. If it feels hard and unmovable, it’s probably fake because it has a hard center. However, if it’s a real moss ball, you should feel it being squishy since there’s nothing solid at the center. When you squish it, water may drip out and about like a sponge, so make sure you do it over a fish tank, or else that store owner is going to really not be happy.

Where to Buy a Marimo Moss Ball

Buy your moss ball from a reputable source.

Buy your moss ball from a reputable source.

Most people will buy them from pet stores and major chain retailers but are completely unaware of the high amount of fakes that exists. Store owners don’t know as well. Or they may completely know about it but expect you not to know about it. That’s why you need to use those pointers up above to make sure you pick out a healthy ball.

Generally, moss balls are priced based on their size. If the deal seems too good to be true, it’s probably because they’re fake. Small moss balls that are about 1” across generally range from $1-1.50 a piece.

Larger ones that range from 2” inches can go $4-5 a piece. Giant marimos can go anywhere from 2.5-3” and can be up to $13 a piece. If the price seems too good to be true, it probably is.

There is a bad practice of sellers, especially online, that basically take one moss ball and rip it into pieces and reform them into many mini moss balls. They state that they’re all original and not appendages from a torn apart giant ball.

This basically gets them many moss balls to sell for the price of one. Sadly, this is hard to detect if you’re buying online. If you’re in the store you can use the pointers we gave you above to easily find out if the owner seller did this.

But if you’re buying them online, it’s going to be very difficult to tell if the seller has any shady practices. In fact, if you’re going to buy balls online, you can’t really practice any of the tips we give you above rather than simply looking at the pictures, however, this will only do so much as you can’t really do any inspection by just looking at pictures and because pictures can easily be fixed. They could have easily stolen them from someone else or just simply downloaded random images of perfect moss balls from the internet.

We’ve had a lot of people ask us questions like why their moss ball isn’t growing or why it’s changing color and we often ask where they bought it from. The majority of the time, it’s the internet. There a lot of sellers online that sell these for cheap and because of bad practice.

They can sell them for so cheap because they’re either fake or simply torn apart into multiple moss balls. You need to watch and steer clear from these sellers and make sure you do your research before you make any purchases online. In person, it’s a lot easier to identify the fakes so that’s what we would suggest for you to do when you make your purchase.

Our Online Marimo Store

buy marimo moss balls

Marimo moss balls craft a zen-like environment.

Since this is a topic that we got a lot of questions on, we have decided to sell own moss balls online. You can check out at our marimo shop here.

We’ve decided to work with suppliers to import directly from the lakes of Taiwan, Japan, and the Far East- directly from the source. We certify that all our moss balls are 100% authentic and native. This will be a surefire way to guarantee you’re buying from a trusted source. The marimos we sell are real, healthy, and authentic.


We hope this guide answers a lot of your questions regarding these fuzzy algae balls. They’re a great species to play with and escape with. And they make a great addition to fish tanks, and they thrive and do well on their own as well. We often see them as a centerpiece for many end tables and desktops. You can add them to a planted tank or have them in their own aquarium.

If you paid attention to this guide, you can easily take care of your balls because you would see that the care isn’t that intensive. They’re low-maintenance species and make a great addition to brighten up and add some kind of entertainment value to whatever fish tank or aquarium or another centerpiece you decide to add them to.

marimo moss ball aquarium

Moss balls can be used on their own as a pretty display.

We think the recent break out in popularity is due to chain pet stores carrying the product now and people becoming aware of them. People walk into a pet store become intrigued by the floating green fuzzy ball and wonder what it is. People that do research and end up in places like where you are right now.

We wrote this guide to help you decide to make the purchase and get yourself a healthy set of moss balls. Or if you’re new to the hobby, maybe you just want to order one for now. Take care of it and it will offer you zen-like qualities as it really works of art for you to admire daily.

I, Anthony, and Rob hope that you can take pleasure in the ownership of these fuzzy little as much as we do. Be sure to check back often as we update our website with care guides, new products, marimo news, and other marimo related stuff every so often. We’re still a new site so bookmark us (CTRL + D)!

Please consider sharing this article

If you’ve learned something from this article, please consider sharing it.

From one marimo lover to another, it really helps out and educates people before they make their purchase, and helps them take proper care of their moss ball as well.

You can use the social buttons below or at the top of this article.

Ready to buy your marimo moss ball?

If you have any questions, you can send us a message. We reply as fast as we can to help you out.

If you’re ready to purchase, please check out our shop, we sell marimos by trusted vendors that we’ve personally verified, or that we’ve sourced ourselves.