Hair Algae / Thread Algae

Clinical Identification

The manifestation is unmistakable: fine, green, hair-like threads weaving through the aquascape.

• Textural Variations: Spirogyra feels slimy to the touch and easily breaks apart, whereas Oedogonium presents as shorter fuzz directly attached to plant leaves, and Rhizoclonium appears as coarse, wool-like green or brownish mats.
• Trophic Impact: Massive blooms act as a net, capturing detritus, uneaten food, and inhibiting water circulation around the host plants. This suffocation rapidly leads to chlorosis and the physical collapse of delicate macrophyte structures, particularly fine-leaved species like Hemianthus and Vesicularia.

Etiological Triggers

1. The CO2-Light Disconnect: The classic trigger for filamentous green algae is intense PAR combined with inadequate or fluctuating CO2. When light drives plant metabolism faster than available carbon can sustain, plants exude excess sugars (photosynthates) into the water, which hair algae rapidly metabolizes.
2. Nutrient Imbalance (The Liebig Minimum): A severe deficiency in a single macronutrient (most notably Nitrate, NO3) stalls plant growth. With the higher plants metabolically arrested, the remaining abundant nutrients are consumed by the less biologically complex algae.
3. Iron Toxicity/Excess: Disproportionately high levels of micronutrients, specifically unchelated iron, have been empirically linked to rapid outbreaks of Oedogonium.

Intervention Protocols

• Mechanical Extraction: The lack of true roots makes physical removal highly effective. Twirling the filaments around a rough wooden skewer or a dedicated algae brush allows the aquarist to harvest massive quantities of the algal biomass quickly.
• Chemical Modulators: Spot treatment with liquid carbon, such as Flourish Excel (Carbon), is effective against Oedogonium but less so against large Spirogyra mats.
• Algivorous Remediation: Caridina multidentata (Amano Shrimp) and Crossocheilus oblongus are exceptionally effective at eradicating hair algae, often stripping an infested tank completely clean within days if stocked in adequate numbers (1 shrimp per 2 gallons).

Homeostatic Prophylaxis

1. Carbon Optimization: Synchronize CO2 injection with the photoperiod. Ensure a 1-point pH drop relative to degassed water before the lights activate, utilizing an efficient diffuser and a reliable CO2 system.
2. Nutrient Loading Stability: Prevent nutrient bottoming out by implementing a daily or every-other-day dosing schedule using complete fertilizers like APT Complete (APT 3) or ProFito.
3. Plant Mass Dilution: Maintain a heavy planting density (covering at least 70% of the substrate). High plant mass provides a vast sink for nutrients, actively starving nascent algal spores of the resources needed to form filaments.