Marimo Moss Ball: Care, Lighting, Water Quality

Marimo moss balls are green algae in the shape of a ball that resembles a plant. Though, most aquarium stores sell the moss balls as aquarium plants. Stores sell the balls as Marimo Algae Balls, Marimo Algae, Algae Balls, Japanese Moss Balls, Cladophora Balls, Seaweed Balls, or Algae Balls.

Even though it’s an alga, it’s not the type of algae that spreads throughout the aquarium. The algae in a marimo moss ball do not turn tank water green.

Marimo Moss Ball Video

Adding marimo moss balls to the tank helps soak up bits of nutrients from the water. Nutrients that would otherwise promote the growth of undesirable algae.


Marimo moss ball care is easy. Place the moss balls in an aquarium and let them float or sink to the bottom. A single moss ball is ok. But, you can add as many as you need so long as the aquarium dimensions (space) allows it. Marimo moss balls do well in established, filtered aquariums.

Marimo moss balls’ growth rate is slow, but once the water quality is good, they get bigger and bigger over time. In tanks with a good current, the ball moves around, which is good. Moving around prevents the moss ball from flattening on one side. In tanks with little to no water current, move the moss ball around from time to time to prevent it from flattening.

Water Parameters

Water Temperature: 72 – 78° Fahrenheit
Aquarium pH: Varies (slightly acidic or on the alkaline side)
Aquarium Lighting: Varies (low to high light)


Debris can build up on the outside of marimo moss balls. But, the debris is easy to remove. Take the moss ball out of the tank and squeeze it in a bucket of aquarium water. You can also swish it around a bit in the bucket.

Don’t worry too much about destroying the shape as you can cup it or roll it in your hands to make it round again.
The moss ball may float after you put it back into the aquarium, but once it soaks up a bit of water, it should sink again.

Aquarium Animals That Like Moss Balls

Marimo moss balls give aquarium animals something to explore, hide behind, rest under, and feed on.

Freshwater aquarium shrimp like the Amano shrimp, whisker shrimp, and red cherry shrimp scavenge for food on moss balls.
If you keep pets crabs, then they too may pick bits of food from moss balls. The same is true for aquarium crayfish.