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.

Document Hair Algae / Thread Algae with close and wide images, check whether the material detaches, and measure light, nutrients, flow and organic load over time.

Compare Hair Algae / Thread Algae with other algae, cyanobacteria, biofilm and mineral deposits using texture, location and microscopy when useful.

Oedogonium is a genus of freshwater macroalgae. In the reported study, most isolates could not be identified to species level using DNA barcoding or taxonomic keys.

The listed conditions are associations to verify in the individual aquarium, not universal causes or operating thresholds.

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.

Wind out strands, thin the densest biomass, and review photoperiod, plant growth and detritus before attributing the growth to one nutrient.

Manage Hair Algae / Thread Algae with physical removal, targeted pruning and documented correction of light, flow, nutrients or organic load. Any product requires its official label and compatibility checks for species, plants, invertebrates and biofilter; no dosage is provided here.

Prevent new Hair Algae / Thread Algae growth with regular maintenance, healthy plant biomass, proportionate lighting and gradual measurement-based changes rather than universal targets.

Act urgently if the bloom coincides with distressed animals, a major oxygen drop, suspected toxins, or detectable ammonia/nitrite.