Green Spot Algae
Hard circular spots on glass and slow-growing plants.
Low phosphate. Add small amount or dose balanced plant fertilizer.
Scrape off weekly during glass cleaning.
Brown Diatoms
Common in new tanks. Brown dusty film on everything.
Resolves on its own in 1 to 2 months as silicates deplete.
Otocinclus catfish love eating it.
Black Beard Algae
Dark tufts on leaves and equipment.
Indicates unstable CO2 or flow issues.
Spot treat with Seachem Excel or hydrogen peroxide 3%.
Hair Algae
Long green threads.
Excess light or nitrate. Reduce lighting duration and do water changes.
Amano shrimp eat it.
Blue-Green Algae (Cyanobacteria)
Slimy sheets, smells bad.
Actually bacteria, not algae. Caused by low flow and excess waste.
Erythromycin treatment, increase flow.
Green Water
Free-floating algae tinting water green.
UV sterilizer clears in 72 hours.
Or 3 day blackout covering tank completely.