Cyanobacteria
Cyanobacteria in Aquarium
Cyanobacteria
A slimy mat-forming photosynthetic bacteria commonly mistaken for algae in freshwater aquariums.
Quick answer
What to know first
- Cyanobacteria forms slimy blue-green, dark green, or nearly black sheets and mats rather than normal algae strands.
- It often starts in dead zones on substrate, hardscape, or plant surfaces where waste and low flow collect.
- A strong smell, trapped bubbles, and sheets that peel away are important clues.
- Siphon mats, improve circulation and oxygen, and reduce organic buildup instead of treating it like ordinary hair algae.
Quick diagnosis
Do you have Cyanobacteria?
You probably have Cyanobacteria if...
- It forms slimy sheets or mats that can peel away in pieces.
- The color is often blue-green, dark green, or nearly black.
- A musty or swampy smell may be present.
- It often starts on substrate or low-flow areas with organic buildup.
- It does not behave like loose green strands or normal dust algae.
Not sure? Compare it with Green Water, Surface Biofilm, Bacterial Bloom.
Quick facts
The useful details
- Category
- Cyanobacteria
- Growth form
- Slimy mat
- Main color
- blue green / dark green
- Attachment
- moderate
- Removal difficulty
- hard
- Main trigger
- Cyanobacteria commonly takes hold in stagnant, dirty, or otherwise unstable areas where sheets can spread quickly.
- Most affected area
- Substrate, low-flow surfaces, and plant bases
Complete guide
How to Identify, Remove, and Prevent Cyanobacteria
Cyanobacteria is not normal filament algae. It forms slimy sheets or mats that can be blue-green, dark green, or nearly black, often with a noticeable smell.
It commonly starts in dead zones on substrate, hardscape, or plant bases where organic waste collects and circulation is weak.
How to Remove Cyanobacteria
Siphon mats out carefully, remove trapped debris, improve oxygen and circulation, and correct low-flow areas. Treat it as a slime-mat and water-quality problem rather than ordinary green strands.
How to Prevent Cyanobacteria
Keep substrate zones cleaner, avoid stagnant pockets, maintain steady filtration, and reduce excess organic buildup before mats can re-form.
Fix Plan
Today
Siphon out slimy mats carefully, remove trapped debris, and improve oxygen and circulation.
This Week
Find dead zones, clean organic buildup from substrate areas, and keep flow reaching problem spots.
Long-Term Prevention
Maintain cleaner substrate zones, steady filtration, and enough circulation to prevent stagnant pockets.
Compare before treating
Often confused with
Extra checks
Supporting notes
Where you'll usually see it
On substrate, plant bases, and low-flow surfaces as slimy mats.
Why it shows up
Dead zones, organic buildup, and unstable conditions allow mats to spread.
Check this before changing everything
Check flow, oxygen, trapped waste, and substrate cleanliness.
Common context
Often seen in stagnant or organic-heavy areas.
Internal resources
Useful tools and lessons
FAQ
Cyanobacteria FAQ
What does Cyanobacteria look like?
Blue-green, dark green, or blackish slimy sheets that can spread quickly across substrate, glass, plants, and hardscape. You will usually see it on substrate, plant leaves, and rocks, wood, and hardscape.
Why does Cyanobacteria appear in an aquarium?
Cyanobacteria commonly takes hold in stagnant, dirty, or otherwise unstable areas where sheets can spread quickly. Although hobbyists call it algae, cyanobacteria is biologically bacteria, which is why it behaves differently from many true algae problems.
Is Cyanobacteria harmful?
Cyanobacteria is not normal algae. It can smother plants, trap waste, and signal low-flow organic-heavy areas that need prompt cleanup.
How do you remove Cyanobacteria?
Siphon out the mats, clean the affected zone, and improve circulation immediately. Physical removal plus correcting dead spots and instability is the core fix; severe cases sometimes need last-resort treatment. Lift and siphon the mats carefully so they do not spread and settle elsewhere.
How do you stop Cyanobacteria from coming back?
Good circulation, cleaner substrate zones, and overall stability greatly reduce repeat outbreaks.
Keep comparing