Brown Algae
Brown Diatoms
Bacillariophyta / Bacillariophyceae
A soft brown coating that commonly appears in newly set-up aquariums and often fades as the tank matures.
Quick facts
- Category
- Brown Algae
- Organism group
- Brown Algae
- Growth form
- Film
- Primary color
- Brown
- Secondary color
- Tan
- Attachment
- Weak
- Removal difficulty
- Easy
Identification
Dusty to velvety brown film or coat on glass, substrate, leaves, hardscape, and equipment.
- Growth form: Film
- Primary color: Brown
- Secondary color: Tan
Looks like: Unlike dark green or black films, diatoms usually look dusty brown and are much easier to wipe or siphon away.
Where it appears
Typical affected areas
- On Glass
- On Plants
- On Hardscape
- On Substrate
Common contexts
- New Tank
Causes
Brown diatoms are one of the most common early-phase coatings in a new aquarium, often appearing within the first weeks.
Most common triggers
- Classic New Tank Succession
- Silicate Availability Can Contribute
- Low Light Surfaces Often Collect It
Root cause note: In many tanks, diatoms are a temporary maturation phase rather than a long-term crisis.
Nutrient relevance
Balance relevance: Low
Related nutrient issues
- New Tank Instability
Do not overreact to early diatoms if the tank is otherwise progressing normally.
Correction hint: Focus on routine maintenance and patience before making drastic chemical changes.
Treatment
Quick action: Wipe or siphon the brown coat away during maintenance and keep the tank routine stable.
Manual cleaning, patience, and natural tank maturation solve most diatom phases.
Manual removal: Diatoms usually wipe off glass and décor easily and can be siphoned from substrate surfaces.
Difficulty: Easy
Prevention
A mature stable tank with good routine maintenance usually sees far less persistent diatom growth.
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.