Cyanobacteria
Cyanobacteria
Cyanobacteria
A slimy mat-forming photosynthetic bacteria commonly mistaken for algae in freshwater aquariums.
Quick facts
- Category
- Cyanobacteria
- Organism group
- Cyanobacteria
- Growth form
- Slime
- Primary color
- Blue Green
- Secondary color
- Dark Green
- Attachment
- Moderate
- Removal difficulty
- Hard
Identification
Blue-green, dark green, or blackish slimy sheets that can spread quickly across substrate, glass, plants, and hardscape.
- Growth form: Slime
- Primary color: Blue Green
- Secondary color: Dark Green
Looks like: Easy to distinguish from most true algae because it forms slippery sheets and often has a strong foul smell.
Where it appears
Typical affected areas
- On Substrate
- On Plants
- On Hardscape
- On Glass
Common contexts
- Low Flow
- Nutrient Imbalance
Causes
Cyanobacteria commonly takes hold in stagnant, dirty, or otherwise unstable areas where sheets can spread quickly.
Most common triggers
- Stagnant Or Low Flow Zones
- Organic Buildup
- General Instability
Root cause note: Although hobbyists call it algae, cyanobacteria is biologically bacteria, which is why it behaves differently from many true algae problems.
Nutrient relevance
Balance relevance: High
Related nutrient issues
- Imbalanced Nutrients
- Organic Loading
Cyanobacteria often reflects poor circulation and accumulated organics as much as nutrient chemistry itself.
Correction hint: Improve flow and hygiene first, then reassess nutrient balance rather than treating it as a simple plant fertilizer issue.
Treatment
Quick action: 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.
Manual removal: Lift and siphon the mats carefully so they do not spread and settle elsewhere.
Difficulty: Hard
Prevention
Good circulation, cleaner substrate zones, and overall stability greatly reduce repeat outbreaks.
This page is designed to help with visual identification first, then causes, treatment, and prevention. Actual algae pressure can vary depending on maintenance, livestock, plant mass, light, flow, and nutrient consistency.