Coralline Algae

Visual Diagnostics (Desirable & Troublesome)

• Morphology: Exhibits as hard, flat crusts or nodular formations spreading radially across bare substrate, glass, and equipment.
• Pigmentation: Dominated by deep pinks, vivid purples, and deep reds, driven by the presence of phycobiliproteins (phycoerythrin and phycocyanin).
• Equipment Interference: Unchecked growth heavily encrusts powerhead impellers, wavemaker rotors, and heating elements, drastically reducing mechanical efficiency and leading to premature hardware failure.
• Acrylic Degradation: On acrylic aquariums, removal of deeply embedded CCA can result in permanent microscopic scratches.

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

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

Calcifying Autotrophs

Coralline algae belong to the order Corallinales (Rhodophyta). They are unique among macroalgae in their ability to deposit massive amounts of calcium carbonate ($CaCO_3$) within their cellular walls, adopting an encrusting or occasionally branching (articulated) aragonitic morphology. Reef Ecology: They act as fundamental ecosystem engineers. In the wild, crustose coralline algae (CCA) function as the critical 'mortar' that binds the reef matrix together, preventing structural erosion. Furthermore, CCA secrete chemical cues that are absolutely necessary for the successful settlement and metamorphosis of planula larvae emitted by hermatypic corals.

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

Growth Vectors

• Alkalinity and Calcium: Hyper-proliferation occurs only in environments strictly adhering to optimal reef chemistry: Alkalinity between 8-11 dKH, Calcium between 400-450 ppm, and Magnesium maintained >1300 ppm.
• Seeding Dynamics: Introduction via 'seed' rock or purposeful manual scraping of existing crusts, which releases microscopic viable spores into the water column.
• Illumination Spectra: CCA strongly favor moderate PAR environments biased toward actinic blue spectra; excessive high-intensity lighting often results in photoinhibition and cellular bleaching of the algae.

First decide whether coralline growth is desirable; remove it only from viewing panes, pumps or functional surfaces rather than automatically treating it as a pest.

Manage Coralline 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 Coralline 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.