Green Water

Visual Pathology

The defining symptom is an insidious clouding of the water column with a distinctive green hue.

• Opacity Spectrum: The bloom can range from a slight hazy green tint, slightly obscuring background plants, to an opaque, pea-soup consistency where visibility is reduced to mere centimeters.
• Physiological Isolation: Unlike GDA, which adheres to the glass, Green Water does not attach to surfaces. Wiping the glass yields zero improvement.
• Diurnal Oxygen Swings: The massive algal biomass produces extreme oxygen oversaturation during the day but consumes vast amounts of O2 via cellular respiration at night, threatening the asphyxiation of aquatic fauna.

Bloom Catalysts

1. Ammonia (NH4) Surges: The unequivocal primary trigger for green water is a spike in bioavailable ammonia in the presence of strong lighting. This commonly occurs following a disrupted biological filter, overfeeding, or a massive substrate disturbance.
2. Macronutrient Imbalance: While ammonia triggers the initial bloom, sustained high levels of phosphates and nitrates fuel its exponential reproduction.
3. Excessive Photoperiod / Direct Sunlight: Unfiltered sunlight striking the aquarium glass provides unmatched PAR intensity, rapidly catalyzing the photosynthetic machinery of suspended Chlorella.

Rapid Remediation Technologies

• Ultraviolet (UV) Sterilization: The deployment of an appropriately sized, high-dwell-time inline UV clarifier is the absolute gold standard for eradicating green water. The UV-C radiation (at 254 nm) directly denatures the DNA and destroys the chloroplasts of the suspended algae as they pass through the chamber, typically clearing the water in 3 to 7 days.
• Flocculation: Chemical water clarifiers act as flocculants, binding the microscopic cells into larger clumps that the mechanical filter media can trap. This requires heavy filter maintenance post-treatment to remove the bound biomass.
• Daphnia Predation: In tanks devoid of micro-predators (fish), introducing a large culture of Daphnia magna provides spectacular biological control, as these filter-feeders will consume the phytoplankton until the water is pristine.

Prophylactic Regimes

1. Biofilter Integrity: Never thoroughly wash filter media in tap water. Maintain robust colonies of nitrifying bacteria to ensure any transient ammonia is instantly oxidized to nitrite and nitrate.
2. Light Control: Avoid situating aquaria in direct sunlight. Utilize timers to maintain a consistent 7-8 hour photoperiod, and manage intensity using capable dimmable LED systems.
3. Regular Maintenance: Conduct 50% weekly water changes, utilizing products that condition the water properly, to mechanically remove suspended organics before they can trigger a bloom.