Gda

Green Algae Powder (GDA — Green Dust Algae)

Scientific name: Chlorella sp., Chlamydomonas sp. (unicellular green algae) Taxonomic type: Chlorophyta Water: Mainly fresh water Color: Light green, yellowish-green Texture: A fine powder that forms on the glass and flakes off in sheets when rubbed

Appearance: A very thin green film, almost like green grime, on the glass. It first appears on the front glass and then on the side windows. Unlike GSA: it is thinner, more uniform, and covers the entire surface of the glass evenly. When rubbed, it forms “curtains” that fall.

Where is it found?: Exclusively in glass. Rarely in decorations or plants.

Is it dangerous?: No.

Related parameters:

• Phosphates (PO₄): Common with low PO₄ (GDA paradox)
• Light: Thrives in bright light
• CO₂: A CO₂ deficit contributes to

Main causes:

1. Paradoxically, it usually occurs when phosphate levels are very low or when nutrients are severely imbalanced
2. Bright light without enough CO₂ or nutrients for the plants
3. Aquarium in the process of maturing

How to remove it:

• Instructions: Scrub with a magnetic sponge. Note: Scrubbing releases a cloud of green spores; change the water immediately afterward.
• GDA Tip: Let it grow for 2–3 weeks without cleaning the glass, then clean it all at once. Many aquarists report that it doesn't come back after that.
• Biological: Nerite snails are the most effective. Otocinclus also scrape the glass.
• CO₂ Adjustment: Increase CO₂ injection if it is a planted aquarium.
• Chemist: Not required.

Prevention: Stable CO₂ levels, balanced nutrients, regular water changes.

---