Taxonomy and Biological Profile

Derbesia is a highly ubiquitous genus of marine chlorophyte, commonly recognized by aquarists as Green Hair Algae (GHA). It features a siphonous, coenocytic structure similar to Bryopsis, but forms much finer, unstructured, tangled masses. Life Cycle: The organism exhibits an isomorphic, biphasic life cycle, alternating between a sporophytic macroscopic filament (Derbesia phase) and a microscopic, spherical gametophytic phase (Halicystis phase). This complex reproductive plasticity allows rapid colonization of sterile substrates within newly established marine aquaria.

Visual Diagnostics

• Textural Presentation: Manifests as tufts or extensive meadows of fine, vibrant green filaments capable of exceeding 10 cm in length in extreme cases.
• Epiphytic Growth: Frequently anchors onto coral tissue margins, causing intense mechanical irritation and depriving the zooxanthellae of necessary PAR irradiance.
• Algal Turf Matting: Accumulates heavy amounts of suspended detritus and uneaten food within its matrix, creating a self-sustaining nutrient sink.

Trophic Triggers

• Eutrophication: Driven fundamentally by excessive macronutrient accumulation, specifically phosphates ($PO_4$) > 0.1 ppm and nitrates ($NO_3$) > 15 ppm, typically secondary to overfeeding or overstocking.
• Rock Leaching: The utilization of uncured or nutrient-laden 'dry rock' which slowly leaches tightly bound orthophosphates back into the water column over a multi-month timeline.
• Photonic Shifts: Degradation of halide, T5, or LED lighting resulting in spectral shifts towards the yellow/red bands (4000K-5000K), which disproportionately accelerates chlorophyte photosynthesis.

Management Modalities

• Intense Biological Herbivory: Deployment of a robust 'Clean Up Crew' (CUC), particularly Mexican Turbo Snails (Turbo fluctuosus), Sea Hares (Aplysia spp.), and Zebrasoma tangs, which aggressively graze upon the filamentous matrix.
• Fluconazole Application: Though primarily targeted at Bryopsis, high-dose Fluconazole protocols often exhibit strong collateral cytotoxicity against Derbesia.
• Chemical Oxidants: Controlled, ex-display dipping of affected live rock utilizing standard 3% Hydrogen Peroxide at a 1:4 ratio with saltwater for exactly 3-5 minutes induces total cellular oxidation.

System Equilibrium

• Lanthanum Chloride Regimens: Precise dosing of Lanthanum Chloride ($LaCl_3$) to rapidly precipitate and sequester waterborne orthophosphates via mechanical filtration.
• Curing Protocols: Subjecting all dry rock to a multi-week dark curing process ('cooking') accompanied by aggressive water changes and bacterial inoculation prior to display tank introduction.
• RO/DI Purity: Ensuring all top-off and mixing water registers 0 TDS (Total Dissolved Solids) via strict maintenance of Reverse Osmosis and Deionization resin stages.