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Blue-Green Algae (Freshwater)
Cyanobacteria spp.
Also known as Slime Algae, Smear Algae
Bacteria›Cyanobacteria›Cyanophyceae›Cyanobacteria
📍 Worldwide — ponds, slow rivers, aquariums
A blue-green or red-brown slime that coats the substrate, plants, and glass with a slimy, foul-smelling mat. Technically a bacterium, not true algae. Caused by low nitrates, poor flow, and organic waste. Responds to a 3-day blackout combined with the antibiotic erythromycin or hydrogen peroxide treatment.
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Quick Facts
- role
- nuisance — urgent
- cause
- low nitrates, poor circulation, excess organics
- control
- 3-day blackout, H₂O₂ treatment, improve flow and detritus removal
Water it likes
- ph
- 7.0–8.5
- hardness
- 5–25 dGH
- temperature
- 68–86°F (20–30°C)
Legality
No state or federal restrictions on record for this species.
Not legal advice, and possibly incomplete or out of date. Rules vary by state and locality and change over time — always confirm the current regulations with your state wildlife or agriculture agency before buying, keeping, or shipping this species.