Why You Should Have A Marimo Moss Ball!

Written by Jakob

Last Updated on February 13, 2023 by Jakob

As you probably already know, Live plants are great for aquariums, besides they look 100% better than fake plants (cleaning plastic plants is also a pain) or plastic ornaments so why ever bother with anything else? Live habitat provide a stunning environment and even provide a natural filter for the tank. They absorb harmful toxins such as nitrates, excess carbon dioxide and help break down fish waste. Live habitat is also an alternative food source for fish, hosting bacteria and microscopic invertebrates that they can eat.

Some aquarium plants are difficult to look after, especially in small tanks with low amounts of space for sufficient sand or substrate. The Marimo Moss Ball is a life saver for those that want the advantages of natural plants without the hassle. Marimo Moss balls do extremely well in nearly all aquarium environments.

The moss ball is a is a species of filamentous green algae, and is native in lakes found in a varying range of places around the world, as far north as Icelandic lakes to Southern hemisphere countries such as Australia. In the wild, they form by rolling along the river bed. A marimo moss ball is a unique and fairly rare type of the species where algae merges into large green balls that look like velvet ‘moss’, hence their name. 

Some people keep Moss balls on their own in small decoration tanks, or fill them with shrimp and other easy to look after crustaceans, which make beautiful decorations in houses in their own right.


Here’s why you should have a Marimo moss ball in your tank:

1. Moss balls are extremely hardy

There aren’t many ways you can kill a marimo moss ball, but you can try your best and usually to no avail. You really would have to go to extremes in order to kill it, and usually that means taking it completely out of water or putting it into a bucket of extremely salty water.

When you have a healthy tank, that is well looked after the marimo moss ball will live a long happy life! Fish that are constantly grazing are a problem sometimes, but typically it’s only goldfish that will rip a moss ball to shreds.

2. It’s a great oxygenator

Not all aquatic plants are great oxygenators. Just like humans need trees to take up carbon dioxide and produce oxygen in order for us to survive, fish need the same. And a well oxygenated tank means happy fish.

The marimo moss ball is very effective way of quickly increasing oxygen levels in a deprived aquarium, the best example is when you have a stone substrate tank or a tank where you can’t (or don’t have time) to plant rooted fauna.

Just buy a couple of moss balls and let them get to work for your aquarium.

3. It Reduces Nitrates

As explained by our nitrate cycle post, nitrates are produced naturally in the aquarium. However, high levels are dangerous to the fish and the health of the tank. It’s the reason why it is of paramount importance to have a high quality aquarium filter and to do regular water changes.

Whilst these are essential for regulating dangerous nitrate levels, there are several things one can do to improve the health of a tank. The beneficial bacteria and filter-like texture of the moss ball help filter out harmful nitrates.

4. They are very affordable

Probably the best thing about a Marimo moss ball is the price. You can buy them here for as low as $10.

I have four in my own tank and the shrimp love them.

5. They look fantastic

These little beauties can enhance areas of the tank that look plain or boring. Installing features or planting new aqua-fauna can be a lengthy process. If you just want to bring to life one area of the aquarium then the moss ball is a perfect idea.

6. It doesn’t shed leaves

Plants have so many beneficial perks for the health of the tank and for the fish themselves. However, they are hard to maintain, are affected by biting fish easily, and shed leaves a lot. The moss ball will shed no organic matter.

Secondly, they will say green and vibrant all year round. No leaves or matter falling off them means they’re healthy all year round too, and that’s one of the biggest reasons they can be so much more practical than a plant.

7. It’s a living filter

As already mentioned, the moss balls can absorb nitrates and so are deep level filters in their own right. But more than this, they also provide the same filtration effect as a particle filter. The waste builds up in concentrated form that fish and other tank inhabitants eat. Once the waste breaks down, it often sinks into the spongy texture of the moss ball and they help to break down waste and water borne phosphates that then is easier on the filter.

Secondly, the marimo moss ball helps produce beneficial bacteria, in a similar way that the aquarium filter works. This helps the maturation phase of new tanks, where often you need to have the filter running for a week or more at least to prepare the tank for fish.

8. It doesn’t need to be planted

Planting for an aquarium is a pain, let’s face it. You have to choose plants that are suitable for the water PH. Plants that tollerate a certain hardness of water, what type of sand or gravel you have. Any finally, there’s still no guarantee the plant won’t be eaten by the kind of fish you have or even survive. When you finally do find a plant that thrives in your environment, it takes ages to plant the thing and anchor it properly in place.

The marimo moss ball on the other hand, requires no ‘planting’, you can clean teh tank around it. It can’t be uprooted and the fish can do their best to eat it and it’ll still come back to life. For this reason, it’s why I love to use moss balls for the forefront of the tank.

9. Helps Prevent Excess Algae Growth

Technically, a moss ball is identical to a giant ball of algae. Essentially, but having ‘desirable’ algae the moss ball will compete for the same nutrients that normal aquarium algae thrive on. If you’ve got an invasive algae issue, you’ll be surprised

What better way to combat algae than with algae? Marimo moss balls suck up the same nutrients as undesirable algae, depriving invasive algae of those nutrients. I had brown algae growing in my 10-gallon tank, but since wiping them off the glass and adding a few moss balls, they have yet to grow back. Of course, moss balls won’t make that much of an impact in larger aquariums unless you get more a lot of them. I don’t know about killing off algae, but they can help prevent unwanted algae from growing back.

What are the disadvantages?

1. Goldfish are its Achilles heel

It has been reported that goldfish will

2. They are extremely slow growing

Moss balls don’t grow very fast. In fact, it can take years for it to reach its full size. Another disadvantage of the ball is that it will not seed or spread. Often aquatic plants will

Marimo Moss Ball Care Guide:

marimo moss ballLooking after a Marimo moss ball isn’t a hard feat. As mentioned before, they are virtually impossible to kill. They don’t shed leaves, and they are beneficial to any tank. Here’s a simple list of easy ways to make sure it’s in peak health.

Light Requirements

These guys don’t need high levels of light. Unlike aquarium plants, the moss ball will probably turn brown and be a little unhappy if it’s in direct sunlight all day. Being in direct sunlight is the cause of 90% of issues with moss balls.

Plant Feed Requirements

The marimo moss ball requires no extra plant feed.

Water Changes

Moss balls can thrive in dirty water. They’re hardy after all, but not doing regular water changes is bad for everything else in the tank. Make sure you change the water frequently when cleaning. Furthermore, you have no excuse not to because you can simply push them out the water when cleaning the sand.

Take the time during water changes to agitate the moss ball slightly or simply place it on another side. This is to make sure it gets an even amount of light all around and also to retain its round shape.

If it floats or looks ill

Don’t worry if you see the moss ball floating. This doesn’t always mean it’s died. More often than not it’s because air bubbles have become trapped in the ball. Simply squeezing the ball lightly in water will release the air. Sometimes this can occur

If your moss ball looks ill, this isn’t because it’s hungry! You should keep the moss ball out of direct sunlight. If you see areas of large black or white spots on it then gently remove these infected areas of the moss ball. It’s as simple as that.

How to Add A Marimo Moss Ball to your Aquarium:

Firstly, as mentioned in the care guide, gently examine the moss ball for areas of white or brown growths. Gently remove them if you see any patches. This stops the infection from getting worse.

Take some water from your tank in a container and use this to rinse the moss balls. Using chlorinated water could harm the ball. The reason we do this is to remove potentially contaminated water from the ball. Since it’s like a sponge it will hold a lot of contaminated water if this is the case and so it’s more important to do this with a moss ball than it is to do it with regular plants.

Additionally, rinsing the ball in this way removes any creatures or snails along for the ride.

Now you can add them to the tank. This isn’t fancy, just drop them in and they’ll float for a little bit before sinking. Again this is just due to air bubbles in the ball. We like to use the moss balls in the foreground of the tank. If you have shrimp or livebearing fish, a few of them together provide valuable food sources and also a safe haven.

If you have a marimo moss ball, or have any questions please get in touch or leave a comment below!


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