Marimo moss balls are not moss at all — they are spheres of filamentous algae that roll gently in the current. They are nearly indestructible, clean water, and make a charming, low-effort addition to any tank.
Light and CO₂
Low to medium, indirect light. Too much direct light can encourage nuisance algae to grow on the ball's surface, so keep them out of hot, bright spots.
Substrate and planting
None needed — they roll free on the substrate. Just place them down and let the filter current tumble them occasionally.
Care and trimming
Gently squeeze and rinse them in old tank water every few weeks to remove debris and keep them green. Turn them occasionally so all sides get light.
Pro tip
If a marimo starts browning, rinse it and roll it back into a round shape; a little patience restores the green. Never boil or scrub hard.
Good tank mates
Safe with shrimp, snails and peaceful fish. Avoid rough cichlids that may shred them; most community tanks are perfect.
Troubleshooting
Brown or floating balls usually mean trapped air or debris — squeeze them out in tank water and they will sink and green up again.
More in our aquatic plants hub.
Light and CO₂
Marimo Moss Ball: The Round, Slow Green Pet has specific light needs. Most easy aquarium plants thrive under moderate LED lighting for 6–8 hours a day; add CO₂ only when you want denser growth. Too much light without balanced nutrients is the fast track to algae.
Planting and placement
Anchor roots in the substrate or tie rhizomes to rock and wood — never bury a rhizome. Place taller varieties at the back and rosette or carpeting plants toward the front so every leaf gets light. Good placement reduces melt and algae competition.
Trimming and propagation
Trim regularly to encourage bushier growth and stop plants shading each other. Many stem plants propagate from cuttings, while runners and daughter plants spread on their own. A trimmed tank stays healthy and looks intentional.
Troubleshooting algae and melt
New plants often shed old leaves while they adjust — that is normal melt, not failure. Persistent algae points to an imbalance of light, nutrients and CO₂; cut light hours and keep up water changes to regain control.
Light and CO₂
Marimo Moss Ball: The Round, Slow Green Pet has specific light needs. Most easy aquarium plants thrive under moderate LED lighting for 6–8 hours a day; add CO₂ only when you want denser growth. Too much light without balanced nutrients is the fast track to algae, so start conservative and increase gradually while watching for green dust on the glass. A simple timer removes the guesswork and keeps the photoperiod consistent, which plants prefer far more than a variable schedule.
Planting and placement
Anchor roots in the substrate or tie rhizomes to rock and wood — never bury a rhizome, or it rots. Place taller varieties at the back and rosette or carpeting plants toward the front so every leaf gets light. Good placement reduces melt and algae competition and makes the tank look designed rather than random. Leave swimming lanes open in the centre so fish are not forced to brush past foliage constantly.
Trimming and propagation
Trim regularly to encourage bushier growth and stop plants shading each other. Many stem plants propagate from cuttings, while runners and daughter plants spread on their own. A trimmed tank stays healthy and looks intentional, and you can often grow enough surplus to share with fellow aquarists. Use sharp aquascaping scissors and cut just above a node for the best regrowth.
Troubleshooting algae and melt
New plants often shed old leaves while they adjust — that is normal melt, not failure. Persistent algae points to an imbalance of light, nutrients and CO₂; cut light hours and keep up water changes to regain control. Add a few algae-eating invertebrates only after fixing the cause, not as a substitute for balance, or you simply move the problem around the tank.
