Filamentous algae are among the most common—and for many, the most frustrating—types of algae found in aquariums. Recognizable by their bright green color and fibrous, thread-like appearance, these algae often grow on surfaces like plants, driftwood, rocks, and decorations but struggle to develop on smooth surfaces like glass. Despite their bad reputation, filamentous algae shouldn’t be seen solely as a problem but as a warning sign of imbalances in the aquarium’s ecosystem.
Why Do Filamentous Algae Appear?
The presence of this algae is often linked to unbalanced nutrient levels in the water. Key factors include:
- High phosphate levels: Typically caused by overfeeding, fish waste, or decomposing organic matter.
- Low nitrate levels: In planted aquariums, plants quickly consume nitrates, leaving excess phosphates.
- Excess light: Overly strong or prolonged lighting, especially natural sunlight, can encourage algae growth.
Filamentous algae act as indicators of these imbalances. Instead of treating them as an enemy, it’s essential to address the underlying causes and restore the aquarium’s balance.
Nutrient Balance
Maintaining a healthy aquarium requires careful nutrient management. In planted tanks, recommended levels are:
- Nitrate (N): 10 mg/L
- Phosphate (P): 1 mg/L
- Potassium (K): 15 mg/L
- Iron (Fe): Between 0.5 and 1 mg/L
When these values are out of balance, algae thrive. The solution lies in regularly testing the water and adjusting feeding, fertilization, and water changes as needed.
How to Remove Filamentous Algae
- Manual Removal:
- Carefully remove all visible algae. Use tools like tweezers or brushes to clean decorations, driftwood, and plants.
- Trim affected leaves if they cannot be cleaned to encourage healthy new growth.
- Large Water Changes:
- Perform a 30-50% water change to reduce phosphate levels and other accumulated compounds.
- Siphon the substrate to remove organic debris that feeds algae.
- Test and Adjust Parameters:
- Use test kits to measure nitrate, phosphate, and other nutrient levels.
- Maintain a nitrate-to-phosphate ratio of 10:1 to prevent algae from outcompeting plants.
- Anti-Phosphate Resins:
- In non-planted tanks, anti-phosphate resins are a quick and effective solution. They absorb excess phosphate, making it harder for algae to grow.
- Fertilizers and Glutaraldehyde:
- In planted tanks, regulate fertilizers to maintain nutrient balance. If necessary, use glutaraldehyde in controlled doses to eliminate algae. Be cautious, as it can harm sensitive plants like mosses and ferns.
- Light Deprivation:
- If the problem persists, turn off the aquarium lights for 5-7 days. This weakens the algae by preventing photosynthesis.
Algae Eaters
Introducing algae-eating organisms can help control filamentous algae:
- Snails and shrimp: Excellent cleaners, but they need trimmed algae to consume effectively.
- Fish like Siamese algae eaters: While helpful, they may not completely remove long algae strands.
Prevention
The best way to prevent filamentous algae from returning is to maintain a balanced and well-kept aquarium:
- Weekly water changes: Replace 20-30% of the water regularly to avoid nutrient buildup.
- Controlled feeding: Feed only the necessary amount to prevent leftovers.
- Lighting management: Use moderate lighting and adjust its duration according to the aquarium’s needs.
Chemical Solutions
If all else fails, algicides may be an option. However, they should be a last resort, as they can harm snails, shrimp, and other aquarium inhabitants.
With patience and care, filamentous algae can be eliminated. The key is addressing the underlying causes and maintaining a healthy, balanced aquarium ecosystem.
