Green Algae
Dark Green Film
A darker flat green coating on glass or hardscape that can become more obvious over time in bright tanks.
Quick facts
- Category
- Green Algae
- Organism group
- Green Algae
- Growth form
- Film
- Primary color
- Dark Green
- Secondary color
- Green
- Attachment
- Moderate
- Removal difficulty
- Moderate
Identification
Flat darker green film or patina that spreads over exposed surfaces more as a coat than as dots.
- Growth form: Film
- Primary color: Dark Green
- Secondary color: Green
Looks like: Closer to green algae coats than to GDA or GSA, but darker and often more persistent than a light dusty film.
Where it appears
Typical affected areas
- On Glass
- On Hardscape
Common contexts
- Too Much Light
- Nutrient Imbalance
Causes
Most common on long-exposed hard surfaces where bright light and mediocre balance let film algae thicken gradually.
Most common triggers
- Strong Light
- Maintenance Inconsistency
- General Imbalance
Root cause note: This is usually a practical appearance label within the broader green-coat category.
Nutrient relevance
Balance relevance: Medium
Related nutrient issues
- General Imbalance
Often points to a tank that is almost balanced but still accumulates flat algae on exposed surfaces.
Correction hint: Tighten the routine before overcomplicating the diagnosis.
Treatment
Quick action: Scrape or wipe it off and watch how fast it returns under the current maintenance routine.
Routine cleaning, reduced light pressure, and stronger biological stability usually improve it.
Manual removal: Most variants can be removed with scraper or pad, though some become more tenacious over time.
Difficulty: Moderate
Prevention
Do not let bright hardscape surfaces sit in strong light without enough maintenance or grazer support.
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.