How to identify and control common planted tank algae by type: black brush algae, cyanobacteria, hair algae, and spot algae — causes, removal, and prevention.
Key Takeaways
How to identify and control common planted tank algae by type: black brush algae, cyanobacteria, hair algae, and spot algae — causes, removal, and prevention.
Algae appearance in planted aquariums is a problem many aquarists face. While algae seem like a "villain," they actually signal environmental imbalance—a warning sign your tank needs attention.
Accurately identifying algae type narrows causes and solutions. Instead of "algae appears → use medicine blindly," think: "What type is this? → What caused it? → How do I fix it?"
Characteristics: Black to gray fluffy patches on leaf edges, rocks, and driftwood. Won't come off easily when touched.
Cause: Phosphate accumulation is primary. Phosphate builds when filter debris, overfeeding, and substrate debris accumulate.
Treatment: Apply wood vinegar (50% dilution) directly to affected areas (remove from water 30 seconds → rinse). Siamese flying foxes eat it, but results vary. Fundamentally, reduce phosphate via filter cleaning and increased water changes.
Characteristics: Blue-green to dark green sheet-like or film coating. Has distinctive earthy smell. Peels off by hand but recurs easily.
Cause: Nitrate and phosphate accumulation plus weak water flow in dead zones.
Treatment: Increase water flow, boost water change frequency, reduce lighting (complete darkness 4-5 days also works). Commercial "blue-green algae removers" (copper sulfate, bacteria-based) work but watch toxicity to shrimp.
Characteristics: Long green thread-like growth on plants, driftwood, rocks. Light growth can be pulled out by hand.
Cause: CO2 deficiency, excessive light, and nutrient imbalance combined.
Treatment: Review CO2 levels, reduce lighting duration, increase water changes. Yamato amano shrimp are known to eat this.
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Characteristics: Green dots scattered on glass and leaf surfaces.
Cause: Excessive light is primary. Most common in tanks with direct sunlight.
Treatment: Physical removal with scraper or plastic card. Reduce light or block it.
Characteristics: Thin brown film on glass, rocks, and leaves. Frequent in early setup phase (2-6 weeks).
Cause: Excess silica during initial setup. Common before filter bacteria establish.
Treatment: Usually resolves naturally after setup. Yamato amano shrimp and plecos eat it.
Three common prevention basics apply to all algae types:
Algae-eating creatures (Yamato amano shrimp, freshwater amano shrimp, Siamese algae eaters, plecos) help, but don't rely on them alone—combine with environmental improvements.