Green Algae
Green Water
Commonly Chlorella, Ankistrodesmus, or Scenedesmus spp.
A bloom of microscopic green algae that turns the water column cloudy green instead of coating surfaces.
Quick facts
- Category
- Green Algae
- Organism group
- Green Algae
- Growth form
- Suspended
- Primary color
- Green
- Secondary color
- Yellow Green
- Attachment
- Weak
- Removal difficulty
- Moderate
Identification
Uniform green water haze or opaque bloom that reduces visibility throughout the aquarium.
- Growth form: Suspended
- Primary color: Green
- Secondary color: Yellow Green
Looks like: Unlike surface films or dust algae, green water is suspended in the water column rather than attached to surfaces.
Where it appears
Typical affected areas
- On Glass
Common contexts
- New Tank
- Too Much Light
- Nutrient Imbalance
Causes
Green water blooms when suspended single-celled algae take over the water column in unstable conditions.
Most common triggers
- Microscopic Algae Bloom In Unstable Conditions
- New Tank Imbalance
- Temperature Or Nutrient Swings
Root cause note: Once a true bloom is underway, simply tweaking one water parameter rarely clears it immediately.
Nutrient relevance
Balance relevance: High
Related nutrient issues
- Water Column Nutrient Imbalance
This problem often reflects an unstable water column rather than algae growing from one specific leaf or surface issue.
Correction hint: Reduce bloom pressure, then re-stabilize the tank rather than constantly chasing the bloom day by day.
Treatment
Quick action: Reduce bloom pressure and consider blackout or UV-based cleanup if the bloom is severe.
Blackouts, UV sterilization, and restoring system stability are common practical solutions.
Manual removal: Because the algae is suspended, scraping surfaces will not solve the problem.
Difficulty: Moderate
Prevention
Keep young tanks stable, avoid major nutrient swings, and do not overdrive light during weak plant uptake.
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.