Brown Algae (Diatoms)
New tank common. Brown coating on glass and décor.
Cause: high silica + new tank chemistry. Self-clears in 2-4 months.
Otocinclus catfish eat them — natural cure.
Green Spot Algae (GSA)
Small green dots on glass. Common.
Cause: low phosphate. Add phosphate fertilizer (KH2PO4) to spot reduction.
Bristlenose plecos eat them but don't fully clear.
Green Dust Algae (GDA)
Fine green coating on glass.
Cause: high light + nutrient imbalance. Stable nitrogen + phosphate prevents.
Black-out method: lights off 3 days. Bacteria die off, glass cleans.
Black Beard Algae (BBA)
Dark fuzzy patches on plant edges, décor.
Cause: unstable CO2 in planted tanks. Stabilize CO2 = prevention.
Treatment: liquid carbon (Excel) targeted on patches with syringe.
Hair Algae
Long stringy green strands. Often on hardscape or plant leaves.
Cause: high light + low nutrients (nitrate especially).
Treatment: increase nitrate to 20ppm, add liquid carbon, manual removal.